I came accross this thread, and thought I'd chime in. I just did a SBC into an LT1 F car as well (1994 Firebird). Things to note in my swap were keeping all the stock accessories and use a SuperRam intake manifold and stuffing it all under the cowl without cutting it.
The SuperRam upper plenum is a piece that the late, great, John Lingenfelter made for testing but never sold. It was reduced in height slightly and the throttle body is on a bit of a downward angle to fit it under the cowl. He used it on an LT1 engine, of course. I happen to get ahold of one of these when I was at his shop for work one time, about a year before he died.
Here are links to pics and more info. It's somewhat incomplete at the moment, since I'm not finished yet. The car is on the road now, runs well. Right now I am dealing with all of the electronics incompatabilities, such as speedo, tach, etc.
http://nostar.net/?q=node/2 http://nostar.net/gallery/vroom
Doug