need to know if 86 CRX side skirts will fit a 91 hatch. also if the rear bumper will fit from the crx to the civic?

Not without modifications.

I've been looking into doing the exact opposite of what you are planning (putting a '91 Civic HB body kit on my '86 CRX SI) The lower part of the body on these cars are similar, but not similar enough to where you can just simply swap over parts.

Why would you want to do that anyway when there are so many body kits available for your HB?

i second that!

nope..sorry bro ..and for what it will take to get it to fir porperly you should have just bought something for the civic