Gregmatic

OK, I searched and scanned the FAQ and couldn't come up with an answer. I have an 89 si hatch (B-pillar seat belt) and am looking into swapping on a door from a 90/91 (integrated door seat belt). I am aware of the obvious seat belt issue differences but want to know if just the whole door itself will fit.
I had a 90 CRX that I had tried to put an 89 door on and it actually wouldn't fit at all, slightly different length. I was hoping to just remove the seat belt assembly from the donor door and use the original B-pillar belt. Any info is greatly appreciated!