I had a buddy with an 80% PF45 frame and a g41 slide (FWIW the frame is gen 3 and the slide is gen 4), and I had a lone wolf g41 10mm conversion barrel, a few beers later we had a functioning pistol. While it functions 100% I don’t think it’s a viable option. You have to mill out the frame to clear the slide as the lower section of the slide where the spring is held is larger on the gen 4. A 3/4 ball mill will accomplish this with some minor cleanup of the spring channel with the Dremel. This leaves the inner channel of the rail paper thin. Next you have to take the gen 4 guide rod and turn the base down to the diameter of the gen 3 so that it fits the seat in the frame. From there its just some minor polishing and tweaking and your off to the races with a 10mm g41. A lot of work for an extra 1/2 inch of barrel, but its works and has probably 200 rounds through it so far.