Yeah, well maybe I was a little gruff, but look at the moniker under my screen name. I've lived on this rock long enough to be a curmudgeon when I deem it necessary. If it walks like a duck and quacks like a duck, then it must be a duck.
Now, back to your project. I posted the first link just to prove that a BBC can and has been shoehorned into a 240Z. The hideous scoop probably wouldn't be necessary if a guy lowered the motor properly between the frame rails and used the type of induction you're thinking of.
Using a SBC to arrive at the type of power you're contemplating just doesn't make any sense. The bores stock bores are 4.000" compared to any BB with 4.250" stock bores. Larger bores will allow larger valves which will pass more air which will make more hp. Any motor you use is simply an air pump. The more air you pump through it, the more power you make.
Assuming 100% volumetric efficiency, the 496 moves 918 CFM at its hp peak of 701 @6400 rpm's. In order to make that same power with a 383, you'd have to wind it to 8,300 rpm's to pass the same amount of air. That doesn't sound "driveable and reliable" to me. On the other hand, twisting a BB to 6400 sounds quite reasonable to me.
Up to and including 500 hp, a SB is probably the best all-around choice for ease of installation, cost of parts, reliability and power in a small light package. But over 500 starts to get into BB territory in my opinion. It's sort of like asking a boy to do a man's job.