I’ll be interested to see what you come up with. I have a very similar setup and also similar circumstances in my 77 400 with a few exceptions.
I have a 4 core copper radiator that looked fairly new when I bought the car 13 years ago. I think I have a receipt for it if I remember right. Anyway, new cast impeller water pump clearanced, 7 blade 19.5” fan with the Hayes heavy duty clutch. Everything forward of my evaporator core has been replaced which included a sanden compressor, parallel flow condenser and 134a.
My temp used to creep up as you described until I installed the HD clutch (which you already have obviously) and it really slowed the warming up enough that I haven’t let it sit long enough to see how hot it gets now. It takes long enough that I don’t have any issues in traffic. My initial timing is 14BTDC
I also struggle to warm up much past the 160° t-stat temp if it’s cooler than the high 70s and no AC. I’ve considered going back to a 180° just because I don’t think it’ll effect much with me. Even on the hottest of hot days my max without AC is usually about 180- 187 if I’m on the e-way but it generally gets cooler as soon as I exit and RPMs drop.
My only thoughts for my car are possibly the radiator has a small blockage but I’d think that would effect non-AC temps. My other thought is my condenser has approximately 3/4” gaps on the bottom and part of the sides I planned to seal but haven’t yet. You appear to have both of those things covered though.
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1977 Trans Am 400/4speed (swap)
Brian
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