help with pistons and question

The fed, and speed pro pistons are nearly the same as they are in different packages, they are a replacement piston, as for the KB 167's they are a 0 deck type and are a good bit lighter than the other 2, and will hold up as well or better. The stock bore of the 318 is 3.91 so 3.94 is .030 over. Any of the pistons will work but I would go with the lightest which would be the KB's.