Hello, I'm new to the forum but been lurking for awhile. I'm working on 68 Firebird Convertible restoration. I'm considering swapping engines from the current 350 to a 400. I'm still trying to determine what engine I have (previous owner said 350). It appears the engine is not original as it appears to have some later emissions items that the 68's didn't have. Since it doesn't appear to be numbers matching I figured I'd swap for a 400. I've looked around on the site but can't find an article that discusses what Pontiac motors can be swapped into the 68's easily. For instance would a '67 Pontiac 400 Code XJ work? Or how about a '73 big block 400? Also, does it matter what car a motor comes from for instance would a 400HO from a '68 GTO work? I don't know much obviously about this engine swap, I'd just like to get some more HP and have the installation be something manageable. I've read some about LS swaps and I don't want to go that route as I'd like to keep the car period correct within reason. Any help directing me to threads already on the forum would be appreciated as I haven't had much luck finding any. Thanks ahead.