the 187s are 305 swirl port, probably 58cc combustion chamber, the other two listed are 72+cc chambers, i personally wouldnt use any of them, almost certain the smog head 882s will work better than what you have listed, find some others
do you already have the intake? personally, i would look for a set of vortec heads and intake, probably get the best performance outta stock parts with vortecs opposed to what you have listed
Buy some Vortec heads and a summit vortec intake. You gain power and efficiency. That means fuel economy. Keep the valve lift under .470" with stock vortec heads. Sell your other heads on craigslist, or 12th street scrap. Buy and use the Felpro # 1094 head gaskets and the premium intake gaskets. Sell the 750 carb on here or craigslist. Buy a good Q-jet or a 600 cfm carb.
Race 355's with a 650 Holley can run low 11's, you don't need a 750 on a PU truck.