look for a 350. anyone will fit. if its a z28 everything is there for it already, everyhting is a direct bolt on from your old engine (water pump, alternator, p/s, a/c, whatever)...
jegs has a crate 350 that is carbed and makes 330hp.
http://www.jegs.com/cgi-bin/ncommerc...28&prmenbr=361
it is a grand more though.
http://www.jegs.com/cgi-bin/ncommerc...27&prmenbr=361
put a manifold/carb on that and there you go.
just a few options.