I assume your talking about upgrading the engine/mission to 99-00 si spec?
You need..
engine/mission
mounts 94+ teg upper drivers all the rest off the si should work.
shift linkage
throttle cable
axles and intermediate shaft(should be on mission)
ecu you can get you 93 ex chipped to dohc spec or get a hondata
the cat may need to be shortened/lengthend
I think thats it.