Re pinching at 2-3 gallons and toast at 6-7? Jeez! You should get 10-12 gallons from one of these better engines before needing to replace it or service it.
To the OP - send the engine to a reputable engine guy and have them look it over if you're not entirely sure what it really needs. To just freshen an engine up is one thing - if you're replacing the everything but the crankcase and head, then yeah... duh.. replace the engine. If you're just changing bearings or so, hell yeah just do that instead!