Don't use the GM transmission. Go with either the AW70 or 71 series automatic tranny from the 200 and 700 series. The Aisin Warner transmission is the same as the BW35 and 55 tranny used in the Rover 3500 auto and the TR8. Except it is a 4spd overdrive instead of a 3 speed like the BW35/55. Get the Rover 3500 or TR8 automatic bell housing. Try to use the Torque Converter from the AW 70/71. Remove the AW70/71 bell housing and bolt up the BW35 bell housing from the Rover 3500 / Triumph TR8. You will then have to figure out the motor mounts, etc. if the earlier Volvo uses the BW35 or 55 you can keep it and just change the bell housing as necessary to the Rover's. The one you currently have on the engine may work as well? I don't know as I haven't look at the Range Rover bell housing except I think it uses a ZF auto tranny. You may want to see if the Rangie's auto trans will fit the Volvo directly as it will most likely be geared better to the engine. Hope this helps? Good Luck!