and it should be pretty easy to see what one you need to shave, (if you need to do so) the front lip on some can be larger than other, and you may need to file it down.
however pics would really help.
You shouldn't have to trim at all. Try working the mag in and out of the mag well a few times. Most poly mags will "shave" a little material off of themselves, where they hang up. Might take a little elbow grease, to get them in the first few times! FYI, this is pretty common with low end AKM's, and low end mags. Even some "high end" AKM'S will do this with certain poly mags.
wasr's are designed as single stack AK's and are dremeled out by Century to use std AK mags, and are snug quite often. try several types of mags and if all are real snug you may need to slightly dremel out the mag well
Arsenal, Saiga (converted), VEPR, or anything that has been overhauled by Rifle Dynamics or Krebs Custom.
note: just because it is a WASR doesn't make it a bad gun, but in the spirit of answering your question I left out all the nuances of Romanian, Yugo etc lower end AKs.