No.
Arbitrarily moving your cam without knowing where it is to start with is a mistake. If you're going to go to all the trouble of pulling the front cover off and messing around with that, take the time to degree your cam. You can't just "guess" at what you're doing...well, you can, but you're pretty much wasting your time. If you find that you're within a couple of degrees of where the mfgr says to put it, then you aren't going to get much by moving it, at your power and performance level. I agree with what's been said about your impeller cut, and the fact that you've probably raised the power level to an unusable rpm with your current combination. The power's probably there, you're just not seeing it. A 750 is certainly big enough for what you're doing. Fords, because of their rod/stroke ratio respond better to a smaller carb that something like a BB Chev. You could try the 850, but if you can't pull that impeller past 4800, I think you'll waste your time there, too. You need to get your motor up in the 5300-5500 range to take advantage of what you've done to your motor. You can keep the vac carb, just put the lightest spring they make in the vac diaphragm, or get a DP.