So how do you guys get the bolts in the rear of the intake manifold torqued down correctly? I can barley get my hand back there?

 

Extensions and a swivel joint.
Not the most accurate, but you can get it close enough.

 

When I replaced my intake plenum and spacer gaskets I ran into the same problem. No way was my torque wrench fitting into that space between the upper plenum and firewall. (4.2L V6) I used a 1/4 flex ratchet and used an educated guess. Not the most accurate, but you can get it close enough.