392's also can be found in the f/s pickalls. The 345 heads will only work on a non-improved cooling 392. There is a serial number cut-off on 392 engines between the ic and nic changeover. Also, you need to take into account which type of pistons the engine has, as in flat-top or dome. Heads that don't match the piston style can cause clearance issues. If you do a forum search, you should come across a recent thread which covered these issues in more depth. Imho, unless you already have some outstanding 345 heads ready to go, the tiny almost negligable bump in compression simply isn't worth all the bs. My advice is to either freshen up your 345, or find a suitable replacement 345/392 that is complete and go with that. If you do swap in a 392, you will need to retain your Scout II oil pump/pickup, oil pan, flex plate, starter spacer and motor mounts and swap them over to the 392. Also, not all IH engines were cast with the same motor mount bosses. Before you plunk down money on one, be sure to verify that it's been drilled to accept the sii mounts that are near the front of the engine on either side.