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

dartjack said
All the pics are a fuzzy as to the tranny clearance to the fabbed in crossmember. Would anyone have a close guesstimate on that?

Well since you are fabricating the crossmember its what ever you want it to be.

In my case about 3/8" maybe a touch more.

Also dinging in the floorpan ahead of the crossmember was mentioned.

Yes, so the engine maintained the exact same location and angles as factory.

Can any of the original crossmember be left in place?

Not really unless you want to cut up the floor and change the drivetrain angle which opens up a slew of problems. You won't be able to use the inner holes anyways due to the width of the overdrive unit.