threaded stems for 1" forks are gonna be 7/8" (aka 22.2mm) or a narrower 21.1mm, common on American bikes from the 60s on and cheap bikes. Threaded stems for 1.125" forks are gonna be 1" (aka 25.4mm)but what will you mount the seat too? With a 7/8", you could just hack off the horizontal part and maybe, I guess, put guts on there if it's a round 7/8" all the way up to where you cut, but if the quill is 1" in diameter, I don't see where the seat goes....