ask patricks about the 4 speed saginaw tranny swap. that requires a little more work. shortening torque tube by 2.5 inches and a yoke conversion. but with the right saginaw(there were several) i have heard an easy 75 mph w/ the 3.55 rear conversion.
"it's only old if you can't find a use for it; otherwise it's cool and i'll use it."
