Likely you already fit your seat with that wide of a tunnel...... I was thinking there was a reason the tunnel is somewhat narrow aft of the transmission.
Yes, 2012 Challenger buckets. They fit, it’s tight but clears. The T56 is huge. With the tunnel in and the trans raised in place, I have about 1/2 clearance all around between the tunnel and the trans.
the tunnel does narrow down at the same angle roughly as the trans gets narrower. Then I tied it into the remainder of the factory tunnel in the rear floor pan area. I’ll put the seats in tomorrow and get some pics to show just how tight it is. Reminds me of how tight the drivers seat in a Humvee is to the trans tunnel
