I like the idea of starting with and ruling out the simple stuff first. I frequent the 460 forums and the below link is one with many thoughts on a similar sounding issue (obviously on a 385 series engine), if helpful. The Mad Porter contributor there is a premier big block engine builder, his advice and troubleshooting is generally of high value. Again, there may be simpler things to rule out before some of these considerations. However, if certain build and tune specs are unknown (cam, springs, timing, etc.), it’s feasible that one of more such issues apply.
https://www.460ford.com/threads/engi...00-rpm.231217/
Best of luck. Brent