Jack, I have a stock 351 crate motor wlth over 5000 track miles and I consistantly shift at 6500 just as I hit the rev limiter. Your engine should easily rev to 6000+ rpm's.Rpm's are usually limited by valve spring float or cam profile, maybe your engine needs more fuel. BTW the Nascar guys spin these motors to 8000+ all day long.
Keep on checking.
RD
