I say if you wanna go small block then 327. If you want a fast small block then stroked 383 or a 400. Either that or get a Chevy inline 6 250 motor or something and fix that up with fuel injection and noone around you would have something like that and you can still smoke small blocks when built right. www.inliners.org is a great site. A bit of those guys drag racing inline 6's and know a ton of pros and cons and can help you out.
Those would be my choices. A Caddi will cost you more money in the end.