Don---Now you can see the sense in my old post about gluing the 1/2" long sections of sawed up broomhandle to a dummy transmission case, (which is bolted to the engine and mounted to the chassis). Then filling in the gaps between the glued on peices with drywall plaster, then glassing over the whole thing to create a tunnel. It sounds a bit hokey, but its pretty foolproof. When I did the tunnel on my glass 27, I hadn't painted the tranny when I got to the tunnel building part, so I used the actual tranny that was going in the car---it all cleaned up when I prepped the tranny for finish paint, later----and I had a perfect uniform 1/2" gap all around the transmission between it and the tunnel.