Is the starter on a 6.2 bolted to the bell housing or the block. Reason I ask is because I want to look at an engine with the auto tranny removed. Can I start it?

I believe there are exceptions, but usually the automatic 6.2L powered trucks had the starter bolted to the engine block.
One exception I think, and dont apply to the truck you are looking at, is the 4spd man.

Recently helped take a 700R4 out of a 6.2 C10 suburban. the starter was on the block.

The starter is mounted to the block. The two main mounting bolts are at the starter drive end and you have a smaller bolt on a bracket at the other end of the starter to provide support as the starter is very heavy.