HOLLEY 750 Vs 600 on a 77

When i aquired my 77 Vette 350/350 autobox the seller told me there was a 750 d/p carb fitted!!?and tubed headers.Since then the engine has been rebuilt with Edelbrock perplus CAM/lifters,h/d camchain,h/d oilpump.Still has original manifold,do i change this for a ALLOY one,which one?and do i need the 750 on it,or is it just wasted and wasting petrol.Ive purchaced a 600 carb as a spare,should i fit this instead?What power gains etc would i get,i use the car nearly every day in summer and travel to shows upto 300 miles away and don't go dragstripping!!!!

I just recently built the L48 in my 76. I bored it .030 over, TRW 9.5 / 1 flat head forged pistons and rods, polished crank, comp 268 cam, heads worked, 202/164 with screw in studs and push rod guides, double roller chain, ZZ4 intake manifold and ignition. I had an Edelbrock 750 on it. It ran good but I felt that there could be better throttle responce. I changed it to the 600 cfm, and what a difference. The throttle responce now is like night and day. if you feel that with the 600 you still need more fuel it is easy to just jet it up.
Worked for me anyway
JoeB