Did you add anything in the way of structural steel over the top of the trans? Or just sheet metal? Unless your getting rid of the torsion bars there needs to be some significant reinforcing of the torsion bar crossmember...
I personally have seen a vehicle which had the center removed for a 518 conversion that while being rolled off a trailer the drivers side torsion bar tore the crossmember loose from the floor & the LF of the car collapsed... The car didn't even have an engine n it... The loads generated by the suspension are transferred into that crossmember & when the car is bouncing down the road that can be some pretty serious stress
I would probably put some 1/2"x4" flat plate over the top & make sure it's burned into the tops of both sides of the crossmember...
