Occasionally I read where someone has had success running a fast rate hyd cam with hyd lifters and carrying the power into the upper rpms.

Particularly in a BB application, in 31 years of dyno testing....... I have never experienced that.
In any brand of engine.

Usually in a BB, they’re “done” before 6k.

Success at high rpm with a fast rate hyd cam/hyd lifters in a BB would be the rare exception..... rather than the rule.

All that being said........ that’s not to say that curing the high rpm capability of your motor would.......without changing anything else...........make huge impact on the ET.

If you have an adjustable valvetrain already, the down and dirty test/solution would be to install solid lifters on that cam and run the lash at like .004-.005.
You’d need lifters and pushrods.
Provided the springs are good, that would buy you somewhere between 700-1000 extra rpm.