I know the xe268 fits in a stock piston 318- I ran one for a few years, I ran it with a 2,400 stall and 3.91's.

My current 318 has the crane .467/.494 but I have KB167 pistons with valve reliefs, I have some warmed up #302's on it and a 833/4.10 rear, it makes pretty good torque, I built it for a truck and ended up sticking it in my Dart, it likes shifted around 5,400.