1967 was a one off year for the F-100, I have one. They came stock with the 352 and cruiseomatic MX, or the 300 big inline 6 with 3 on the tree. I've seen one that was special order with 428 and 3spd..but that was a special order.
Porting and polishing valves is never a bad thing as long as you dont overdo it, I did it on my old 8BA flathead and it made alot of difference. I think as far as heads go, your stuck with stock unless you do another bore and go the edelbrock route.