Depends on what you want to do with it use wise. If you simply want to run it as a mild street engine it sounds like someone has put some work into building it and it might just run with a little cleanup and some new gaskets. If you want to have it as a high performance engine you should probably disassemble it all the way down to a) see what components and work are in there, and b) to check clearances and specs to see if it was done really right.

It's always a crap shoot going into a motor or a car someone else has built. There are all levels of skill when it comes to this stuff and I hate to trust someone elses standards and workmanship. All that it would cost you is a new complete gasket set and you should be able to tell a lot once you start opening it up. You will know if it has ever been started, and if not, how ready it is to fire up and stay together. There are markings on the backside of the cam that will identify what it is, and if it is suitable for the intended use you have for the motor.

When I bought that Camaro ex race car a while back I tore the motor down all the way and it was like reading a book on what the engine builder did. I saw grind marks that told me the engine had been balanced, found race only components that I didn't want to use like a mechanical cam, and also that the engine evidently ate up a cam lobe and lifter during break in. If I hadn't gone all the way through it and tried to fire it up I would have done more damage because of all the metal fragments from the cam.

So, I'd tear it down, find out what you have, and put it back together with new rings and gaskets (with whatever components you deem suitable for your use) and call it good. You will sleep better at night and also know your new motor a lot better. The reason I suggest rings is that they may have lost tension from a long storage.......same maybe with the valve springs.

Don