Neil is right on the money DD. Upgrade the unibody, rear end, suspension, and brakes to handle what you intend to put in it. TBH my "fun car" 2007 mustang GT has a 300hp 4.6L V8 5 speed and 3.55s and it pretty freaking fast as it is. It will peg 140mph, and idles great. I dont need to go any faster than that. 500hp is a lot on the street especially without electronic nannys. I know hellkittys are like 700hp, but they also have the added benefits of yaw sensors, active suspensions ABS, and TCS which help Joe average to drive it like a pro. What I'm trying to say is 500 hp you may hit that mark, and many do, and then they dont enjoy driving the car as much.
Not trying to tell you how to build the car, but going to explain the nuts and bolts of the one I am building with/for my son. 69 barracuda coupe so basically a 108" wheelbase dart. 3200 lb car. We added subframe connectors, upgraded to big bolt pattern with cordoba big calipers and discs, ford explorer 8.8 with discs, and a hellwig 1&1/8" front sway bar. The usual polyurethane bushings all around etc.
Now to the drivetrain. It will be a 300hp warmed up 318. Yes a 318. Trans is a 42RH with lockup and O/D out of a V6 1992 Dakota. This trans has 3 mechanical forward gears like your 3 speed automatic so your stock floor shifter can be retained. The O/D and lockup are electric. I went 42RH which is A904 based for several reasons. 1 they can be built to handle up to 500hp so behind a 300hp engine it will be reliable. 2 they are smaller and lighter than the 46RH. And 3 the 1st gear gearing is lower than the 46RH to help a V6 truck pull a load from a standing start. Turn the lockup and O/D on above 55mph with a toggle switch, turn them off below 55mph with the same switch. The rear end gearing is 3.73 along with 25" tall tires on 15x7 chrysler steel rims.
Whats in gearing? A lot. With the 300hp, 3.73s, and low first gear gearing that the 42RH has, this things gonna be really quick in first thought 3rd gears, and a 300hp 318 will not be real cantankerous to run. At 75 mph on the highway with the lockup and O/D turned on and the RPMs will sit at about 2400 rpm. Best of both worlds, on a rock solid chassis with good brakes and mostly stock parts with enhancements and upgrades.
Again not telling you how to do your build. Just explaining our build, and showing you a different option you may not realize is out there. A lot of times, or dare I say most times, it's not all about just absolute horsepower, but about a carefully selected package of horsepower, gearing, suspension, brakes, and chassis. I have a long winded build thread. Not sure if you looked at it. 67/68/69 cuda dilemma. All the information is there on the 42RH install mockup, and soon the 318 buildup once the block is out of machine shop jail. I feel the combo of (lower levels) of HP which is easier to build, and with better idle and driving manners, along with the rest of the package will make for something that's fun to drive, and not a chore to drive.
Matt
. the BPE 408 can be bought quite a bit less than 10k too, if you reuse some ancillaries from your old motor.
over 20 years!
