The 95 will have an HO engine, different then the older AMC/Renix sytem. Different head, electronics and wiring. Not a straight swap but its been done.
Is your '91 a HO or non HO engine? I think '91 or '92 was the change over year.
Easiset way I can think of to tell is does it say 4.0 HO on the back or the HOs have a temp sensor in the t-stat housing, the renix systems have them in the rad.