For just driving around I'd run 87. I had a 69 318 2bbl coronet 440. I took it to the track flipped the air cleaner and advanced the timing. tossed in 5 gallons of 93 and ran 15.69's. My 95 5.2 Dakota w/ MP ECM would rattle it's brains out if you didn't run 91. I'd get unleaded 107 at the track it ran 14.07. I think the 71 has lower compression than the 69.