I am purchasing an M1 thompson, From what I can gather they will not take surplus wartime mags without some modification. I know the drums won't work(Don't care) just want good 20 and 30 rnd sticks. it is one of the newer Kahr arms version. Anyone with one care to enlighten me? source for good mags etc... Spare parts to keep on hand? (I intend on a firing pin and springs at the least.)