the only common pb threading that MIGHT work...
phantom (acme, PITA to do without a special insert)
uncommon pb, but possible, 7/8-20 (ccm tips, lapco tips), freak tip (7/8-32 double lead)
for the price of buying a unibody, then having it rethreaded, you are already over the price of a new breech and barrel
Ryan “Super_Stanchy” Stanchfield