454 Tear Down - When to Stop?

[Rat72]

It's been a long saga but the seller of the motor said it was freshly rebuilt about 10 years ago and then garaged. I got it running (barely) but it had almost no vacuum and I had to run it way advanced to keep it idleing. When I pulled the plugs, everything was fouled so I put some new plugs in it and tried to set the timing to something reasonable. But it didn't run any better.

So I pulled the manifold and found that one of the lifters had come apart. I installed a new cam and lifters but went to check the plugs before reinstalling the manifold and two of the plugs had oil on the threads and the tips were covered with carbon. This is after running it for about 2 minutes. The other plugs looked OK including the plug where the bad lifter was. So I hate to button everything back up if there is a bad ring or valve or head gasket. Whata you guys think, do I have a problem or is it just the remnants of all the bad timing and previous fouling? My thought is to run a leakdown test on her? Thanks in advance for any insight.

Whit