What parts are different on the 88 dx and si model on the rear suspension?

I know the trailing arm is different, but what else.

I have to replace the crossmember because of a recent wreck on my dx, and am cosidering replacing the entire rear suspension from an si. (That way I have disc brakes)

 

So you mean 90-91 Si correct?

 

1988 Honda CRX have a eye socket on the LCA
1989-1991 Honda CRX have a fork socket on the LCA

 

yes that is correct

and if I could've gotten the 88 I could of used a type r suspenison I had laying around

but those are hard to come by sometimes