340 Timing / CAM Issue
I would change the oil and filter, replace the cam.....a good used one would be ok but use new lifters. find a manifold and run it.
I know that's a Hacked way of doing it. but if you pull the pan, you will need to put a new oil pickup, then rebuild oil pump or replace.....then bearing need to be replace because your in there.
And before you know it you just rebuild a vary questionable block!
IF you put a cam in it and it make a year or two.......then it may be worth a rebuild.
Just a thought.