Original coil will probably work.When I installed this setup,The original Bosch blue coil was fried,hemorrhaging oil down the side and breaking down when hot.I bought the pretty polished stainless Hot spark coil along with the electronic conversion,since it needed one anyhow and to cover my ass if there were problems.6 mos or so later,owner called and said her car just quit suddenly on the highway,in rush hour traffic.
I head out look at car,no spark,coil doesnt ohm right.Hot Spark coil sure looked to be good quality,but I have seen sudden failure before.Even on Bosch. Hauled owner up to O'really's,where of course we got the usual "72 MBZ? we have to order it". Seems about everything Euro ran a Bosch bluecoil for years,so I told them to look up a coil for a 1972 VW Beetle,for which they had a China's Finest in stock.$20-ish. Just temporary while she checked warranty on Hot spark coil,and she was on the side of the road,so what the hey.Popped it in, fired right up.Never heard from her again till head gasket gave out.Car still ran great when I pulled the head.As long as the coil is the right ohm range on the primary resistance,the ign doesnt care (up to a point).I run 3 German made Nology coils for a Harley on my KZ 1300 drag bike,primary resistance was perfect.... Just find orig hot wire to coil + where it screws to a resistor on driver fenderwell.It lowers the voltage to reduce arcing of points.Wire around resistor so coil gets a full 12 volts to + term.The 2 wires from dist just go to coil.red+ black-.I think + is also marked with orange paint dot on the connecter I soldered in.But look,think,and check stuff because this was a while ago and I work on a lot of odd stuff.I only trust my memory so far,and check everything if I go back. Timing will need to be reset afterward,same as with a new set of points.Wrench on, Dan.