I have no idea what the stock specs for that engine would be. Most of the stock late 80's early 90's sbc's I've had experience with were not big on power. But if the goal is to just get it running I say, just get it running. Then tune it the best you can to get the most out of what its got. I'm guessing its only making in the low 200's, maybe 250 hp. It should still have a nice seat of the pants feel with the low end torque of even a small V8.
The nice thing about sbc's is that you can buy speed parts for furture builds that will work on the future engine. You might even want to go with a small block in the future, the vehicle should handle better with less weight in the nose. Keep in mind it isn't hard to build a big cube sbc these days. 427 cid out of a sb is no big deal now. There are 470+ cid sbc's now! And there are heads and intakes that will flow enough air to support that many cubes that aren't that expensive. If you put money into headers and exhaust for the 305 now, you could use the same headers and exhaust system on your big cube sbc when its done. Same goes for the intake, ignition, etc... The only thing you really need to keep an eye out for is Vortech versus non-Vortec heads and accessories.
Its alot of fun to dream about speed equipment but running is much better than not running too.
