Safe rpm

Get in it, drive it hard, listen to when it quits pulling hard, or when valves float. That should be a reference point, then start grabbing gears and shift 2-300 rpm lower that. Adjust as needed. Each car is/will run differently, depending on part combination. I've had several 340's, some run like a raped ape, others just run good. Had a few that were dogs, till I figured out what was going on.