Best Bang for the Buck Head???

Torkers are crap IMO. The Air Gap with the 750 DP will be the best power producer, but the 1406 Eddy carb would likely deliver better mileage. As for the cylinder head question, I think having your X heads worked over a bit would be the best bang for the buck. Good valve job, nail head intake valves, tulip exhaust valves, clean up the bowls and short side.