New 482 Tunnelport wont rev

[Smokin427]

We have tried everything and are totally stumped. Built a 482 Tunnelport in a 56 Ford and trying to get it going. It will not wind above about 5200 and takes forever to get there. Has no power at all. Does not miss just feels like a small 4 cylinder. We have checked all the obvious stuff such as:
Timing and advancing (New MSD ingition, 16 initial 32 total (it is advancing))
Rods at .0025 and mains at .003, Took only 32 lbs torque to turn it over, Compression is 190 to 200 on all, Battery turns it over easily so nothing is frozen,etc. Carb is a new HP850 and seems to be working just fine, No vacuum leaks as far as we can tell. Plugs look good, Cam is an Isky custom grind solid lifter cam and set with the dot on cam gear facing the 0 on the crank gear. It is only .540 lift, ~242 @.050 and had plenty of valve to piston clearance. Even checked it with open headers in case the exhaust pipes were somehow blocked but it makes no difference.Had problems with using shell lifters and longer pushrods with the pushrods binding in the intake port tubes but replaced them with std solids and std length 3/8 hardened pushrods and there is no interference now. It has roller rockers also. The engine is not making any wierd noises, it just does not want to accelerate !
It is absolutely blowing our minds !
Has anyone ever experienced anything like this and if so, do you know where we might look next ?