I've got a 350 from '71 and I was curious as to what it's redline is? Also I'm wanting to take it on the expressway but sometimes tranny won't go into third gear and I was wondering what damage am I going to do (besides eat gas) if I run the engine at 65 mph for about 15-20 minutes in second gear? TH-350 transmission. 3970014 casting number with a 2 bolt main and I have 2.56 gears in the back, if that's of any concern. About 600-700ish miles on new rebuild. Thanks.

with 245/60/15 (26.5 inch tires)
3200 rpm in 2nd gear will give you 65mph

sounds safe to me, but would waste a bit of gas

i am pretty sure you can take the motor to 6000, 5500 just to be safe

Sure, you can take it to 5500, but not for 20 minutes... Unless you like walking home.
Grover