I recently bought a shabby 3270 keyboard, cleaned it up and fitted what spare keycaps I had already:
As you can see, it really needs space and backspace! These are the same as on any Model M, I believe (including the spacebar stabilizer wire).
What you can't see is the Model F spring I've used temporarily in the '.' switch. That works ok for testing, but it's far too soft.
So one or two Model M springs wanted as well please!