78 cop 440 - and this is from the service book that I'm looking at in front of me - has a factory stall speed of 2500-2800. They did this to help offset vehicle weight and smog effect. I know it's a long shot, but if you had one of those laying around, give it a shot. That's a good factory H/D part. I would imagine a 76 and 77 would be the same. Just a suggestion. I know there's a weight and perhaps even a torque difference but if you're making pretty good power, you might get right into the range you're looking for