When I was born, my great grandmother willed me a 1953 Plymouth Cranbrook sedan. For pretty much 25+ years it has been stored in a garage where the flat 6 engine has frozen up. I recently decided to put this thing in running condition again but am having a LOT of trouble with the frozen engine. Dropped it off to a mechanic but after several weeks of soaking in oil and removing top half, its still stuck. Any ideas? Also, what is a reasonable cost range to pull the engine and rebuild it?

Any help is much appreciated!