This an 88-91 CRX right? If so you should get an 89-91CRX/Civic Si tranny, if you can't get one of those get an 89-91 lx/dx SEDAN tranny. After that get a dx hatch tranny. Anything other than that don't waste your time.
AN 89 tranny comes with a smaller flywheel but the flywheel from the z6 or the 90-91 will fit on it. This allows you to use a larger clutch. I am 99% sure you use the clutch for the flywheel you are using.
This is an easy swap, I did it in my old civic.