Novice with a Rebuilt Engine?

[smootma]

Hey guys. I just bought a 4.2L inline 6 that the guy said was rebuilt and had about 4K miles on it. I took off the valve cover and oil pan and although all components look clean and free of junk, the covers themselves have a fair amount of what I assume is burnt oil, some of which has bubbled or flaked off the surface (see attached pic). Does this sound like a rebuilt engine to you? How many miles before this stuff starts to appear on the covers? I also took off the exhaust and intake manifolds and saw some buildup on the valve rods on the intake side. Again, should I expect that at 4K miles? Finally, there's a plate on the side that says it was rebuilt by Capital City. Anybody ever heard of them? I Googled it and couldn't find them. The guy said he thought they were out of DC.

Thanks for any help you can give me.