Do a Gen3 engine(LS1,LS2,LS6,4.8,5.3,5.7,6.0 - take your pick, they all have more power than the 94 engine), you won't regret it. Get a salvage yard engine, a NelsonPerformance engine harness and tuned PCM. You'll need to plumb fuel to it plus install a new high pressure/high volume fuel pump in the tank. Get the Fbody(preferred) or truck exhaust manifolds and you're ready to roll. It's a pretty easy change over. You'll need engine mount adapter plates. Those can be picked up on Ebay for about $40.

The rear end will last forever in a 94. If you don't have limited slip, get one.

The Nelson harness is like 5 wires to hook up. Simple Simon.