225,slant six radiator

If they did a really sloppy job are you sure the fan is facing the right direction? I saw an electric fan get replaced at a body shop that spun backwards and caused fun overheat/ac problems.

There is a plug on the passenger side of the engine to the rear of the oil filter. That is your block coolant drain. If that plug will come out remove it (its threaded) and see what kind of crud comes out. With an unknown engine with unknown previous owners there is no telling what is floating around in there. There could be 5 bottles of stop leak plugging up your block. With the plug out there should about 3/4" of free space before you hit the bottom of the water jacket. It is not uncommon for there to be a layer of sludge built up there. If you find it is full of sludge the easiest fix would be to remove all the freeze plugs and flush everything out with a garden hose. The freeze plugs are on the driver side behind the exhaust manifold, but if you are careful you can remove(and install) a few of them without pulling the manifold.