Here's a good article that will answer most of your questions about what will fit.
http://www.babcox.com/editorial/ar/ar40047.htm
It would be best if you get the computer and wiring with the "95. In late '95 the piston rings were made thinner and moved higher up on the piston. This makes the Knock sensors Very important to prevent piston/ring damage. Does your "91 computer/wiring have one or Two Knock sensors? The '95 will need Knock sensor in each head. If your "91 computer isn't set up for 2 knock sensors you run higher risk of piston/ring damage.