Power advantage between Ford 351, Mopar 340 and Chevy 350??

Don't know, probably none. Ferds only won when the engineering faults were fixed with factory backing, money & engineers; without that they would have won a big, fat...zero.
Another problem was the large two piece 2.19" int valve. Many a time at the old Castlereagh dragstrip I would see a 351C going home on a tow truck after dropping an int valve. The heavy valve combined with the 1.73 rocker ratio reqd very strong valve springs......which two piece valves do not like.