1977 Ford F-150 truck, distributor stuck to 351 engine. How to remove without breaking off?

One mechanic thought it was merely stubborn, tried hammer plus large flathead screwdriver; no luck. His assistant said it may be galvanically corroded to the engine.

Have you had a similar occurrence that you resolved? Any ideas will be appreciated.

The problem will be the rubber "o" ring around the distribitor body that seals it into the block
The can over time actually becone stuck and will require force to shera the rubbe rto get it out
Using wd-40 and continually tristing the body while pulling may get results

Aerosol carb cleaner works well to melt the hard carboned up oil that is gluing it in the block. It takes time but just keep wiggling and spraying and it will free up.

Use Break Fee, it dissolves rust. Worked so well that a stuck mirror is now so Loose, (rust was holding it in place-!) that I need a drop of glue to hold it! Soak overnight, tap back and forth with small hammer and screwdriver on Mounting base Only; tap Down towards manifold before prying up. Use new O ring and grease thoroughly.

The distributor is stuck due to oil varnish deposits, get a syringe and carefully squirt some acetone under the distributor flange to loosen up the varnish deposits holding the O ring and distributor shaft. Nothing will work better then acetone but carb cleaner spray may also work, although not nearly as well as acetone.