I did this on Tuesday of this week! Found a donor 1975 254 at the JY and in about 1/2 hour I had a spare complete system. You need all the associated parts (you can junk some of it later). Here are the steps, first disconnect the coil and note where the wires go...this is the last time you'll be clean. Then unplug the distributor from the wiring harness and unbolt it from the holder on the block (7/16 wrench) then remove the holder and cam drive gear from the block (1/2 wrench) and put this stuff in a ziploc. It is just easier to access the two bolts that secure the holder to the block without the distributor installed.

Then on to the harness. You've already disconnected the distributor, now disconnect the main harness from the "black box" located on the strut tower. Put black box in ziploc. Then find the ballast resistor - you won't need it with the stock coil, but take it anyway, with the coil - it is located under a small heat shield on the firewall, to the left of the brake booster. Then pull the wiring harness back through the strut tower towards the firewall. Disconnect the harness from the main car wiring harness (trace the wires back as far as you can go - cut). There is one wire that is attached to the secruring bolt of the master cylinder (17mm wrench) and removing the coil was 13mm wrench - remember to bring both metric and fractional wrenches when pulling stuff off a '75