Driveshaft length

I am going to do a weekend engine/tranny/rear swap on my Duster and I wanted to get a driveshaft pre cut so it is only down the weekend. ( I drive it to work)

What is in it: 318/904 and 8 1/4.
What is going in it: 340/727 and 8 3/4

Does anyone have a Duster with a 727/8 3/4? I need the to know how long it is from the center of the u-joint to center of the u-joint.

Will the tranny support and everything else from the 71 dart fit in the duster?

Anyone forsee any problems with this going smoothley?