I finished up the exhaust crossmember.  This is just below the seat crossmembers, which are on the top side of the floor.  This crossmember should stiffen up the unibody a bit.

I drilled some holes through the heat shield:

I turned some threaded mounts on my lathe and welded them up into the tunnel.

The mounts line up with the holes I drilled earlier.  The crossmember bolts solid into the body, and the heat shield just covers everything up.

 

Bolted up: