I thought that I read in another thread there was some concern over mating frame to different calibers. I was cleaning my 37 and 35 last night and was looking at similiarities vs. dissimiliarities. Boils down to only the locking block is more heavier duty, but the dimensions appear to be equal from an eyeball point of view. So, put the 35 slide on the 37 frame and 37 slide on the 35 frame. perfect matchup.... dried fired both, no problems. Next step would be to try live fire on the 37 frame with the .40 caliber slide. Other than ejecter, any reason that this should not work? What am I missing here? I can easily see that the GAP locking block is heavier duty, but this may a a plus. I don't think that I would necessarily want to try the GAP slide on a normal .40 frame, but I wonder just the same how it would hold up. etc.