The pistons need to be changed on the a4 and a8, I believe. The K24a1 block doesnt need to have to pistons changed. You can use the stock pistons out of the a2(TSX) or the a1 in your a8 block and use your old rings so you don't have to hone the block. Or just use the a8 longblock to get you running until money becomess avaiable.