Jack:
You stated that you have 2V Cleveland heads on 351 Windsor block. Has the camshaft ever been changed? Is it the OEM stock cam? If it is, 5500 RPM is about the top, regardless of ignition
or cylinder head configuration. I'm asuming the timing is set properly. To move horsepower & torque up the RPM scale you will need too consult with a camshaft manufacturer to get a camshaft with timing specs that will allow the engine to reach
it's RPM potential. Should be able to spin 6000-6500 with a stock
rod balanced bottom end. Regarding one block vs another. The block is just the foundation, it provides the rigidity to support the crank and rod rotating assembly and creates the shortblock assembly; it will along with the quality of crank and rods ultimatly determine the rpm limit of the engine before the crank begins to flex and ultimatly fail.
Rick
