I would have no reservations running 20w-50 in a modest small block. Especially in your Arizona heat.
Obviously too thick for any break in use. But for Arizona street use? Probably the best choice.
I'm VERY interested in first test run of your build. So much similarities to my efforts.
I will certainly post any results from my 451 hit. I'm hoping for 9.90s. But I'm guessing 10.20s. I'm NEVER as fast as I hoped.
MPG is tough. My right foot dictates. 16 MPG is the best I can get on very modest highway driving. Stockish 440 4-speed B-body running Dana 3.54:1 with talker 28" rear tire. But just a couple fun thumps on the pedal and suddenly drops to high single digits. Or worse if nonsense continues. Lol...
3rd gear woes for hard street driving I found to typically be the syncro. (At least started.) And it's not just an A833 thing. I believe its because harder de-accel demands are typical in 3rd gear.
What I don't know. Is if an 18 spline syncros are any tougher than 23?
With Centerforce clutch...
As many has stated. This story, unfortunately is not unique. It shows that a sound "Will and Testimony" can prevent alot of family discourse. But that is also easier said than done. Real estate is actually the easier part of that process. Investments and personal items can be tricky. Just look...
I've never owned a small block Mopar. Most due to circumstances. But I've been eyeing some as late. I was minutes late on a '67 fastback Baracuda 4-speed with its original 273 commando. I REALLY wanted that car!
My current stable is one A-body. One B-body and one E-body. For those looking to enter the Mopar classic car arena for first time? Hands down I recommend A-body. Even though the word is out. And their prices are also rising. They are still best bang for your dollar.
Just my 2 cents.