Slant Six compatability

I am selling off the 225 with autotrans attached out of my 75 Duster to help pay for the 440 install. I have a fella asking me if it will fit into a 66 Dart, and if it does, will he need the drive shaft reworked. The interchange manual that I have only encompasses 68-74. I suspect that the driveshaft may be an issue. Help please.