I only read your post and will tell you to treat it like a 340.
Replace the piston or a new set, the new set should be the KB pistons with a dome for some compression with an open chambered head . I myself like to ounch out the bore as far as possible on a 318. Sonic check it first. Then use a cloased chambered head (Edelbrock for example annd probably with a flat top piston and cam as needed.
Go here for a compression ratio calculator;
Compression Ratio Calculator - Wallace Racing
The 318 can not be bored out to a 340 (4.04 bore size) but may, MAY Sonic check good to a 4.00 bore. That would be 332 cubes. If it only goes .060 overbored, it’s a 327.
Grab the “How to Rebuild a small block MoPar book(s) and go from there.
Have fun