I'm building a big block for my '89. 454, .040 over, 427T heads, just under 9:1 compression, and crane's truck cam for idle-4600 (.485/.485 266/266@.050"). Right now the truck has it's original 700R4. I can rebuild the 700R4 using the tightest tolerances, but I really don't think it will last. I'll be running 3/4 ton axles with 3.73's. With 31-33" tires my rpms at 65 MPH on another transmission (TH350/TH400/SM465/etc) with a 1:1 final drive is from 2628-2469 RPM. With overdrive, I'm only turning 1802 RPM. So, we're looking at almost a 1,000 RPM difference between overdrive and a 1:1 final. Basically, I want to drive 65-70 MPH without my 454 sounding like it's gonna explode. Thoughts, comments, suggestions?