[Excaliber]

The heads could still be a big variable. The only way to know for sure how they work would be to put them on a flow bench.

Your cam:
Recommended RPM range with matching components
Minimum RPM 3600
Maximum RPM 7200
Valve Float 7800

Sounds like you got a bottle neck in there somewhere. The cam does specify 13 to 1 as recommended. This IS a "radical" cam. With my roller, high rise heads and high compression flywheel horse was well over 600 (open headers). Worked out to a VE of over 100%. My rpm range was 4000 to 7000 with valve float at 7400. Pulled strong up to 7000.

It has been shown that the accelleration ramp of the cam profile is more important than the peak lift numbers. If the Blue Thunder heads are not "quite there" at lower lift they would not start working "good" until peak lift. Perhaps, to little to late?

I don't want to be the bad guy, maybe your motor is doing just fine! Just throwing out some possible "anamolies" for consideration. Hard to "blue print" a motor after assembly!