Some PB Blaster, Time, and a Snap-on A144A would be a good start.
http://buy1.snapon.com/catalog/item.asp?store=snapon-store&item_ID=12061&group_ID=1619

Be sure the valves are free before trying, or remove all the pushrods and deal with the valves later.

Also be sure the oil pump turns, we've sheared the tang on a distributor because of a locked up oil pump when turning over a stuck engine.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-