emjay
+1y
you should be fine with the 12v pistons with the 8v head. The main concern is the valve reliefs creating an interference issue using 8v pistons on a 12v application. The F series engines are non-interference engines so unless you jump a tooth you shouldn't have any issues. Just make sure that the valves are in the same position as the reliefs in the piston, and you should be alright.
While the pistons aren't dished as deep, the piston doesn't sit as high on the rod versus the stock B series application so the compression won't increase.