I'm trying to figure out the gearing and tire size, but not sure what the "optimum" cruising rpm for the motor (LQ9/4L80E) is. I realize it's probably about personal preference, but swapping out ring and pinions get expensive, so any information on a cruising "sweet spot" would be appreciated.

 

I like no more than 2100 at 70 to 75 mph. My 54 chev panel has the 80e and 3.00 gears, cruises nice at 80 mph.