If the head is off, leave it off. Drop the short block in place, attach the manifolds to the head outside of the engine bay, and drop the head in as an assembly. Have help to drop the head on if you need it - the head assy comes to around 80-90# or so.
If the head is already on the block, it's time to do some thinking. The lower rear manifold screws are a bastard to get to, although some 6" extensions and a 9/16" "flex" socket (inbuilt universal joint) makes them a bit easier to get to. Still, that gasket is easier to service on the bench than on the engine - so think about it. Since I'd go through a used engine anyhow, it's a moot point for me - the head would already be off. But, it's something that should be considered...