Only 460hp

A full weight duster with a good tune up of the suspension is 11's with a good converter. Me personally, I don't think your that far off except for it nosing over at 5300 but that's not a deal breaker. In the spirit of how I have dealt with a less than stellar HP number it's compression test, leak down the cylinders, vacuum check, and timing. If all that checks out then you can atleast know something is not a miss....

As said, a nice 150 nitrous hit would make your combo a 10 second ride no questions asked....

JW