1968 SS Dart in progress

Well, summer is here again in sunny Arizona and the heat has been no friend to the Dart. I have been wrestling with cooling woes since finishing the build and have gained a bit more knowledge, and appreciation, for what it takes to get one of these a bodies with a 440 BB to cool here in the summer.
The following is a bit lengthy and detailed but a good example of what to do and what not to do in some cases.
I would like to share some of my insight with those of you who are interested. I started my build with a seasoned and stock bore 1972 440 block out of an RV. Instead of boring you with all of the build specs, I can tell you that it produces 525-550 HP. A relatively mild build. I am running A/C (aftermarket).
The first iteration of cooling system consisted of a stock core support opening, and the use of a 26" 2 row aluminum radiator that my Dad had sitting in his storage from a previous build. A brand new 440 source stamped water pump housing and 440 source water pump with correce .040 water pump gasket along with a factory 160* T-stat were installed. An 18" flex-a-lite flex fan and spacer were used due to lack of clearance. I installed an autometer classic mechanical temperature gauge for precision into one of the unused ports up in the water pump housing. The car would heat up to 180* from a cold start at idle in approximately 3 minutes. I know, way too fast! A check of the timing demonstrated a slipped timing ring on the professional products balancer. A new 440 source fluid damper was installed and timing set appropriately with consideration to the cam profile and mechanically advanced distributor curve. All wiring was thoroughly checked from the MSD 6AL ignition box to the ignition coil and it was discovered that the distributor wires were crossed. That fixed the jumpy timing interval issue. So, all of the electronics and timing were sorted out and perfect at this point. Still no help in the cooling department but now the car is tuned properly. All spark plugs within normal burn temperature. I took the Holley 850 double pumper with mechanical secondaries to Bob Reems and had him double check everything as he had built the carb and all flow characteristics and 4 corner idle circuits were within spec. No effect on cooling issue. Then, I installed a Mr. Gasket high flow 160* T-stat which did help the issue but I still could not drive the car in our lovely 105* degree heat with the A/C on without heating up to 240*. It cooled down to 230* without A/C on and would elevate back up to 240* at a stop light. I pulled the used aluminum radiator, inspected it and found that several of the cores were clogged with debris. That radiator went into the recycle bin! It was replaced with a freshly re-cored B body 4-row copper brass unit my Dad had in storage. A much larger radiator in all dimensions measuring in with a 28" core! Kind of overkill but remember, I am cooling a street/strip and air conditioned big block car...IN ARIZONA! An aluminum fan shroud was fabricated and installed. Surely this must fix the problem! Nope, not even close! Ok, back to the drawing board. Upon further inspection it was decided to perform surgery on the core support to expose the entire 28" core to incoming air. This was performed by removing the bumper, grill, trans cooler, A/C condenser, radiator, wiring, etc.. Next, the lower core support with cut along the factory break at the frame rails and lowered 2.5" and the top lip was removed from the core support to allow the radiator to come forward another 1". This turned out exceptionally well and now permitted the use of a factory 17" fan and fan clutch along with the aforementioned aluminum shroud. Airflow across the radiator was increased exponentially and I was sure this would solve my problem. You guessed it, still no good although a slightly longer warm up time was noticed. Talk about frustrating.
A call to Ron Davis radiators here in Arizona netted some vital information to properly diagnose block pressure and flow characteristics throughout the engine. They recommended I purchase an inexpensive water pressure gauge ($11.67) from home depot and install it using an available water port. This is the same gauge one would use if checking their home water pressure from a water spicket. I had already researched water pressure and flow characteristics online but did not think was relevant in light of using brand new 440 source parts. After all, wouldn't new parts perform great out of the box? My research proved otherwise! It turns out that block pressure should run around 15-16 psi at about 2000 rpm. I installed my newly acquired gauge using an available water port and had 8 psi at the gauge 2-3000 rpm! It does not matter if the thermostat is open or closed or if the water is hot or cold with this test according to Ron Davis. In this case Ron suggested I install a factory 160* thermostat instead of the high flow unit in order to promote increased pressure. No change. Next step was to replace the water pump as Ron informed me that most aftermarket water pumps just don't work well. He recommended a high flow Edelbrock but I had already purchased and had on hand a brand new FlowKooler unit along with a Mopar performance aluminum water pump housing "just in case". I assembled them with new Fel Pro gasket, re-used my high flow Mr. Gasket 160* T-stat, painted, and installed them. BINGO! An instant and obvious improvement in pressure to more that 20#'s at 2000 rpm was witnessed. I turned my attention to the flow characteristics through the radiator and WOW! The flow differential at idle when the T-stat opened up was greater than I had observed at 2000 rpm with the 440 source parts installed. It now takes 10 minutes for the car to heat up to 180* at idle vs. the previous 3 minutes and the heat coming off of the top of the engine is noticeably less. The car is still at my Dad's shop where I have performed all of the work. I was not able to take it out for an actual test drive as there were customer cars in the way and he left town for the 4th of July weekend. Dad will take it out for a test drive this week and if things still aren't the way we like them we will have a new aluminum radiator made for it.
The verdict is as follows. In my opinion and based on diagnostic testing, the 440 source parts do not perform well in a mildly built 440. They do not provide enough flow or pressure through the block to prevent steam pockets and cavitation. I reached this opinion by addressing all of the fundamentals in a step-by step, chronological fashion So far I have addressed fuel mixture, timing, performance of the distributor curve under advance conditions, fluid capacity, air flow capacity and air flow velocity at idle and at speed, fluid dynamics relative to mixture, flow, and pressure. I harbor no ill will towards the 440 source company or their products. There are more efficient options!
Included are pictures to show the radiator position prior to modifications. Also, The modifications themselves, and some pic's of the differences between the 440 source water pump housing and Mopar performance water pump housing. My hope is that this will help some people sort through the rhetoric and emotional posting that occurs when trying to find a solution the their cooling woes.
I will post sometime soon with the results of the rest drive, more pic's of the finished product, and details of any other changes made if necessary.