I ran 15.90's at just over 84 mph with a bone stock 318 2bbl. Stock carb, stock exhaust manifolds, stock converter, stock 2.94 gears, stock everything in a B-body. It did have dual exhaust.
I imagine to keep most people thinking it's stock, you could have put a stock 360 2bbl and intake on it, 360 cam, 340 exhaust manifolds, and port the 318 heads. This all would appear stock to your average person but would add up to considerable gains. Then add a better converter and 3.55's. :)