A 496, 502 or 540 are all short deck blocks. The 502 and 540 have the same larger bore. The 540 just has a stroker crank. They all share the same external dimensions as a typical BBC. The web page mentioned above has all the info needed to drop in a BBC. If you go with a tall beck block then there may be additional clearance and fitting problems but 600+ CID are possible.
I'd like a 540 myself.
Your T5 tranny will have to go. GM didn't even put that tranny behind a 350 so it won't last behind a BBC.
My front suspension is still relativly stock. Even though I have a BBC with cast iron heads there's been a lot of weight stripped off the front of the car. The only thing I've changed to the front end are a set of Koni SPA1 drag struts and a set of V6 springs.
Good weld-in sub frame connectors are a requirement but then they should be on all third gens.
Your 92's 10 bolt is strong but a few modifications can make it even better without having to invest in a 12 bolt or 9". I've actually ran 11.2's at 121 mph with a 10 bolt but blew up an engine doing it.
Stephen's racing page
or check out the race car
87 IROC SuperPro race car
461 big block
Best ET on a time slip: 11.589
Best MPH on a time slip: 115.91
Best corrected ET: 11.114
Altitude corrected rear wheel HP: 457
Best 60 foot: 1.646
Member of the Calgary Drag Racing Association