The only front end parts that differ for a '91 Camaro RS vs a Z-28 are the following;

Front lower control arms
Front spindles
Front rotors
Front brake calipers

Everything else is the same. Now, this doesn't mean anything has to be changed. The parts on your car are the same as an RS V-8. The changes are based by model, not engine. The above parts are for changing to a IROC-Z and a Z-28. The springs for all Camaros from '82-'92 are the same. The front crossmember is the same. The struts are the same. The cooling system between all 6's and 8's are the same.

What you do need to deal with is what everyone thinks is easy, and that's the wiring. The fuel injection systems are completely different, and even if a carb is used on the V-8, you'll still need to blend the existing wiring harness to the wiring that will power the engine.

Considering the current gas prices, you may also want to look at a V-6 (not that 3.1L). Maybe a 3.8L or a 4.3L with a supercharger. Either way, good luck.