Well...you could build a 454 CI small block that would be the exact same size as the 327 you have in it now.
I'm assuming you're talking about a roots style supercharger, not a centrifugal. A centrifugal would be pretty easy to fit under the hood even with a big block.
Getting a roots blower under the hood without cutting it...I'd say you're limited to a Weiand 144 or 177 or the newer Edelbrock E-Force blowers (which are made by Magnuson I think).
I doubt you'll fit a big block and a roots blower under the hood without cutting it.
I believe your question should be "How many pounds of boost can I get with a blower, or centrifugal, or turbo, without cutting the hood?". Once you land on that answer, then "How many cubic inches of engine can I fit under the hood with my chosen power adder without cutting the hood?".What is the largest CI engine with a blower that will fit in a 55 without cutting a hole in the hood?