Windsor or Cleveland?
There are two easy ways to tell -- looking at the upper radiator hose and looking at the valve covers.
|351 Windsor 2V||351 Cleveland 2V|
On a Windsor, the water neck for the upper radiator hose is going to come
straight out of the front of the intake manifold. On a Cleveland, the water
neck is going to come up vertically out of the block.
The other way to tell is by looking at the valve covers. If they're roughly
the same shape as the 289's and 302's you're used to looking at, you've got
a Windsor. Windsor heads interchange (mechanically, anyway) with 289's and
302's, and the valve cover gasket is going to be wider at the lower edge
than at the top.
With a Cleveland, the valve cover is going to look more "rectangular" when
viewed from above. (That is, the gasket would be about as wide at the
bottom as at the top.