well, it is a double pumper and that is at least one very big part of the problem as others have now mentioned, and this is why we ask the questions.
imo, i think you are far better off starting with a much smaller carb like a 600 and definitely a vacuum secondary style unless you plan to drag race it a lot and don't care so much how it runs on the street.
it is a bazillion times better to tune a car that has the right size carb than it is to tune one that has a carb that is just wrong in nearly every way.
if you do get another carb, i would not get an edelcrap one. stick with vacuum secondary holley's or quick fuels etc.
also, if you put a smaller carb on it, it is quite possible that it will run just fine even if it isn't 110% perfectly jetted etc. and the money you may save on dynoing it would pay a big chunk of the new carb, PLUS, you can probably get $200.00 ozzie franks for that 750 on gummy tree or ebay etc. ...or shaunp might even give you some credit for it in a trade.
