I think it's more than likely out of cam... That one would make a mean street camshaft. As was suggested... try tightening the lash. If it revs cleaner try retarding it but dont be surprised if it doesnt do much. You're only opening the valves about .545 assuming .020 lash and the usual pushrod angles. You may also try tightening the convertor. 5K is pretty high for a 4" engine with that cam. You'd be better off with cam, more gear, and less convertor IMO.