The problem is that anyone who would pay a lot for an engine is probably a "collector" or serial restorer and will have heard that story before... and then found the "running" engine they bought seized with broken gears, snapped cam chain, bent and broken valves, scored cam, totally disintegrated carb internals, crossthreaded spark plug holes, seized cam chain adjuster, ground up metal in the sump, and a holes punched though all four pistons. So even though you're an honest guy and your engine really is in good shape for the mileage, don't expect anyone to believe it.
Anyway caveat emptor, and if you can flog it for the price you want then more power to you!