I don’t have experience with the 3:38 gears, I do have experience with the 3:55z

I’m running a 302, with Pertronix, dual Zeniths, and a Truckstell .73 overdrive, with Patrick’s 3:55 gears, and 16 inch tires. It does very well and I use overdrive often. This set up in the 45 Art Deco GMC does very well. I’m confident your 302 can handle the 3:38 in overdrive. Log some miles for yourself and then adjust if necessary.

~ Phillip
1949 GMC Suburban - 10 year project
1952 Pontiac Chieftain Convertible straight 8 hydramatic
1945 GMC half ton truck - Driver- Sold 9-15-25
1946 Chevy COE - SOLD 1-5-26 BUH BYE CHEVY!
1959 GMC Half ton long bed NAPCO