Are you in an area that freezes? Also, have you checked freeze plugs?
As far as the engine, the 390 was a work horse. It would be nice to save it, but it may cost too much. If it isn't locked up, I would put clean oil in it with a new filter and some good gas to see if it will run. Chances are it will. The determining factor will be if you have any rod or bearing knock. Expect to hear lifter noise for a short while.
Let me know what you find.
Wednesday, September 21st, 2011 AT 2:42 AM