No spark issue
If it's "ready to run" I would just "hotwire" it to the coil and test it that way. You don't really need it in the car.
Also when you get it going, on connecting the MSD 6 box to the coil: MAKE SURE the ONLY wires to the coil are the MSD plus and minus wires from the MSD box. Do NOT connect anything else including the radio suppression cap or the tach wire.
What is the part no. for the "ready to run" unit so I can look that up?