42RH / A-500 in a Duster with pictures.

If it helps I have photos of a big block A-518 install I did on mine. Very similar to this install except for the reinforcement where the original torsion bar crossmember gets cut out I used 3 inch by 1/2' thick steel and put it inside the car on top of the trans tunnel then welded it 100% My trans crossmember is similar to this but I used a piece of four inch C channel for the trans mount pad. Its a lot of work but the end result is very good. Click on my photo link over to the left of this reply.