I'm still not quite sure why you wouldn't want a 350, but even still, adding a smallblock chevrolet will not add that much extra weight to worry about ride height, etc. Most of the aftermarket built smallblocks out there are going to be 350s, so you may want to reconsider purchasing one, and for the price range you have, you can find one that is very nicely built. Good luck with your search. You can also check out
www.paceparts.com, I'm sure they will have what you are looking for.
Better yet, here's a link with some of the engines they sell :
http://www.paceparts.com/subcat.asp?0=343