Franchi 48 and Browning Auto 5 parts do not interchange. And finding stocks for the Franchi 48 is difficult.....and depending on year of manufacture, sometimes nearly impossible. The older guns, pre 1970's have rear stocks with a collar ring on the mating surface between the receiver and front of the stock. These stocks are damn near impossible to find and command a high price tag when you do find one. Post pictures of the crack and I'll be able to tell you if its worthwhile to repair. Hairline cracks are a common problem with 48's because many people have used the guns with the friction rings set in the incorrect manner for the loads being used. Shooting heavy loads with the friction ring set to the light load setting causes the barrel to violently recoil into the receiver causing the hairline cracks. Adding lube to the mag tube can also cause the same problem. I have repaired more of these stocks that I can count, so its very possible a replacement stock isnt needed