After many years as a Chevy II junkie (I still am), I just bought a 91 RS with the 305 and a five speed to become my next project car. First order of business is to replace the 305 with a 350+ small block. I'm going to scour the threads here for help but thought I'd ask a question to get started. In order to go from the 305 TBI to a carbed 350+, how much modification am I looking at (Fuel system, electrical system, etc)?

It's fairly easy. Electrical is simply clipping most of the wires. Just don't clip the 2 going to the coil. You'll need those. Don't clip any going to the starter or alternator, either.
Fuel system is easy if you're willing to buy a good bypass-style AFPR, because the pump in the tank is pushing 12-15 psi, and Holleys only want 6, Q-Jets only want 3.5.
You will need to upgrade the entire exhaust system. And you will need a 153-tooth flywheel on your "new" engine, to fit inside the T5 bellhousing.
You currently have 2.95/1.94/1.34/1.00/0.63 gearing, with a 3.08:1, 7.625", 28-spline non-posi rear. This means you're doing 1600 rpm at 65 mph, which sucks.
The easiest solution is the complete rear axle assembly from a '90-'92 with V6 and automatic. Exact same, except 3.42:1. Typically under $100. Then install a PowerTrax conversion-style locker.
Your stock cooling should be fine for getting it up and running.

Be prepared for the rearend to grenade. An upgrade might be in your future depending on how much power you will make.

Subframe connectors are also recommended. These cars just aren't stiff enough to plant decent power to the ground.

spoken wisely from another BBC guru!

If you aren't dropping the clutch and powershifting, the rear and trans will both go quite a while. For outright torque capacity, the trans is weaker than the rear. When you break into the 12s, start looking for a stronger trans. When you break into the 11s, start looking for a stronger rear. Please sell your trans before you damage it.

LS2 Dana 60 ;o

I've got my Chevy II for serious bashing. (Turbo400 w/brake).The Camaro will be for street cruising. I just want it to be able to get out of its own way and be fun to drive..

In that case you can just drive it and see what breaks by experiment. No need to spend a bunch of money as long as you don't mind changing things when lessons come your way.