Upgrade engine and pistons

What compression? most slants wind up with the pistons around .250" below the deck and are lucky to have 7.5 to 1 compression. Cutting .100" off the head will get this almost to 9 to 1. Cast pistons will be fine until you add boost or nitrous, so it boils down to what you want to do with your slant. You really need to get the top of the piston closer to the deck than it is right now. That is not going to happen with 225 rods and replacement pistons. If I ever build another one, I would bore it to 3.5" with forged 2.2 Turbo pistons and 198 slant rods. This gets the compression near 9.5 to 1 without milling the head or deck. There is enough metal in the cylinder walls for this much overbore and that is about as big as you can get with readily available head gaskets. You can get the pistons and K1 H beam rods from Campbell Enterprises and when the new found power becomes boring you are ready for boost or nitrous.