Do you guys realize how much of a rip off the modified distributor caps are for external coils?
MSD sells a kit for about $4 to convert it. All you do it drill a hole in the cap, put a long machine screw through it and thread on the terminal. THAT'S IT! LOL
However you do need to modify the distributor wiring to run an external ignition box and coil regardless of whether you buy a cap or make your own.
The MSD is NOT car specific, I have a digital 6 and can tell you if you buy one without big boost you are wasting money. Our ignitions are one of the most powerful stock ones out. 50,000 volt coil from the factory, what the MSD Digi 6 does is increase the current to the coil to make a hotter spark, but not a more powerful one.
Again, there is NO power to be had with aftermarket ignitoins on a SR20 running less than 13psi or so.
Jim Wolf has the schematic on what wires need to be cut and a lead soldered and run outside of the distributor to trigger an aftermarket ign box.
Oh and BTW if you do modify the cap for external coil be sure to cut the stock coil tower off at the base, and fill the hole in the cap with silicone so the spark does not engergize the stock sleeping coilpack.