Yes, the MVI71-DFNT can work in a 1771 chassis with a PLC-2 processor.
Along with the MVI71-DFNT sample ladder, you will need to use the following settings in the PLC-2 programming software:
*The Lengths of the BTW and BTR instructions should be zero. It will default to a 64 word block transfer size.
*2-slot addressing is needed.