Safe, Efficient F/R Brake Bias

[GoreMaker]

I'm planning some brake upgrades for my '77 Trans Am with 400/4-speed. I'm staying with OEM-sized 15" wheels, so my options are somewhat limited. My current plan is for 12" front rotors with Wilwood dual-piston D52 calipers (I'm installing Pro-Touring F-Body tall spindles that accommodate 12" brakes). I'm debating a bit on the rear. I'm definitely planning a Wilwood rear disc conversion, but I'm torn between 11" Dynapro Low Profile and 12.19" Dynalite kits. I'm concerned that the 12.19" would be too much brake compared to the front and shift the bias too far back. The calipers for each kit both have the same piston diameters, though the 11" kit appears to use slightly shorter pads. It's kinda hard to see what the actual pad surface height is for each caliper from the diagrams, so there's a bit of guessing in my calculations, but I doubt the differences are big enough to cause much error.

Whats a safe brake bias for these cars that still maximizes the rear brake efficiency? I was planning to try to stay near or above 70% front, which it looks like the 11" rear kit would achieve, while the 12.19" kit would bring me to about 65% front, which seems inadequate considering how front-heavy the car is. I can get away with 65% on my Buick Roadmaster wagon because its weight balance is about 50/50, but that's definitely not the case on this Trans Am.

Yes I realize I could "fix" the ratio with an adjustable proportioning valve, but I'd like to get it as close as possible using just brake hardware and a regular, stock-looking disc/disc proportioning valve.