NNNnnnnOOOOoooo!

While everything superficially looks clean, the engine will need to come completely apart for a more through cleaning.

Dry ice blasting only displaces dirt and does not wash it away like a solvent bath. This means grit is jammed between cam bearings , piston rings and makes it's way to the oil pan.

Also with the cam being slightly rusted, valve stems would be rusted also. Sure then engine will run as is, but it won't last. Given the engine was "free" he can afford to buy a gasket set and do a proper cleaning / inspection.