I have a 1949 P15 which has not run for 40 years, I have it in the shop and the mechanic says the valves are stuck, he is soaking them in an effort to release them, if he cannot free them and start the vehicle how hard is it to rebuild the motor (are parts available) or has anyone replaced the engine and if so what would be an easy substitution?
They built variations of that engine for 40 years so the parts are still readily available for rebuilding. If the block is good, a rebuild if very practical. That said, the number of shops that are experienced in rebuilding them are declining and some of the parts are getting up in price.
If you decide to swap out, then most 1935-59 6 cylinder Plymouth or Dodge passenger car engine will fit. With a bit more work, there are industrial engines up to the early 1970s that are basically the same design. There were changes along the years including but not limited to width of fan belt, teeth size on flywheel, etc. And the Dodge vehicles with fluid drive had more holes on the crankshaft flange. So mixing and matching parts needs to be done with a little thought.
Thanks for the information, I would like to retain the original engine if possible.