With that much timing in the engine, I'd figure the cam was back a tooth, engines that have cams retarded a tooth like loads of timing right from the start, and usually have very soft low end performance, with acceptable high rpm operation.
Any idea what compression ratio, lifter type, advertized overall cam duration, duration at .050, and what degree does the intake valve close at (do not need lift or other cam specs)?
What are your ignition specs, initial, idle, vacuum advance degrees (let me guess, there either isn't a vacuum advance, or it isn't connected, sounds like there isn't enough vacuum to run one anyway), and total timing (you say it is 56 degrees)?
Cam specs Below
Engine Family:Chevrolet 396-454 c.i. 8 Cylinder (1967-1996)
RPM Operating Range:2,500-6,500
Cam Type:Hydraulic Flat Tappet
Lifter Style:Hydraulic Flat Tappet
Camshaft Gear Attachment:3-Bolt
Valve Springs Required:Yes
Camshaft Material:Cast Iron
California Proposition 65:WARNING: Cancer and Reproductive Harm P65Warnings.ca.gov
Advertised Intake Duration:292
Advertised Exhaust Duration:292
Intake Duration at .050 Inch Lift:224
Exhaust Duration at .050 Inch Lift:224
Intake Valve Lift:0.55
Exhaust Valve Lift:0.55
Lobe Lift Intake:0.323
Lobe Lift Exhaust:0.323
Assembly Lubricant Included:Yes