Hi Bill,
First off, nice choice of airplane you got there!
I just went trough 2 years of “everything” was broken on my car… So I would also prefer the runner but from what you posted you seem to have the knowledge, time, space and are willing to have a project. I had basically no knowledge and managed but not without this forum and the people on it.
I would definitely do a compression check and walk away if that isn’t good. I don’t mind low compressions but they have to be even. Based on my experience any XJ that has sat for a while will have clogged injectors so they wont start. But you could just give it a little break cleaner or start pilot or similar and see if the car comes to life on that. I would try to inject that after the AFM since it probably doesn’t appreciate being soaked.
I had to go through everything including the engine so I would want to make sure the engine is as good as it gets. Of course you have to decide. This is personal. Probably a gut feeling. Good luck and keep us posted.