Using a Buick/Pon/Olds turbo 350 trans. with a 3,500 stall. The crossmember is something I made out of 1"X2" tube and attaches to the 2"x3" frame connectors I welded in to connect to the frame. Pretty simple really and will give me plenty of room for the exhaust to run down the side. I bought a K-Member with no motor mounts and made my own so I could set this all up and be able to move the motor back in the chassis then I cut the firewall and moved it straight back 3-1/2" to give me room to get to my tranny bolts.
In this picture you can see that, I cut the factory wall and just moved it back and added metal to the sides so it look factory still.