My Dart Swinger Project!

If the 360 is in good condition, then maybe that is the way to go. See if you can ask the owner to NOT run it for a half day or more before you get there, and run a compression test 'dry' BEFORE you start it up. In that way, any oil that might help seal bad rings up and make the readings look better will have drained off. Pay close attention to the plugs as you pull them out and look for oil. Then start it after compression readings, and see how it sounds.

I'll tell you one story about how just compression readings can fool you: my '62 Dart's /6 had good cylinder readings on all 6 before I tore it down....1 to 6 were 115-110-120-115-120-115. Those are good consistent readings, just a tiny bit on the low side. But when I tore it down, #1 cylinder need to be bored out .040"! So good compression readings can happen with very worn cylinders, especially when the cylinders are oiling, and even with worn valve guides.

All you can count on is that it will tell you if something is grossly wrong, like a bad valve, but won't necessarily tell you if there is a lot of bore/ring wear, loose guides, etc. With those things, the engine will be down on power and won't run 100% evenly.

As far as head cracks, one of my Opel rally car head had a hairline crack in it, between the intake and exhaust seats in #2 or #2 cylinder. (It was a'73 head, 1st year for the hardened valve seat for unleaded fuel; they tended to crack in '73-'74, like a lot of US made heads did too.) Raced it that way for 3-4 rallies or so; it would run 15-20 degrees hot and use a tad of coolant. It ran fine otherwise, but I replaced it eventually.