mooney
Charles,
There are plenty of excellent engine builders on this forum. Without lots of details they won't be able to give you much help. One builder I know will not spend more than 3-4K for a run-out "core" in order to make the finances come out. However, a "core" means different things to different people.
I am assuming that the engine you are talking about is a 0-360 A1A with a hollow crank. I am not a Mooney expert but aren't they 180hp constant speed with a McCauley prop? If the TT is less than 2K the chances are that the case is in pretty good shape, i.e, no fretting, wear, etc.
One would still have to assess the remaining components; thats why buying a used engine is still tough to do without seeing it. Also, it may be the original engine or it may have been a new engine replacement for the older aircraft. That's why the logs matter.
To back up even further, if you are really wanting to sell the Mooney and it is repairable, you will be able to sell it much more easily if the engine stays with it. Any one buying it (a certified AC) will have to go out and find the exact same engine (per Type certificate) to restore the Mooney. The Mooneys had other issues, i.e. wooden tails etc, that may be a factor too. Point here is that it will be for most a much easier project with the engine on the plane.
The aircraft resale market has been tough where I'm at. The guy in the big hangar next door has had a half dozen aircraft mostly repaired Cessnas and Bonanzas, that he couldn't move, although lately things look like they have picked up a bit. I imagine prices are still somewhat depressed. If selling the Mooney is a priority, your best bet may be to cut your losses and sell the whole package and they take what you recoup and put it into your RV. Only you can decide which way is best for you.
Dave A.