Ballast resistor with a Duraspark

[milocj]

I recently bought a good running CJ with a 304 and a glass body (but a trashed frame) to swap onto my good frame. When I went to hook everything back up I noticed that there was a ballast resistor buried on the firewall, but hooked into the ignition system. I know that the factory Duraspark system is supposed to have a built in resistor wire and no ballast resistor, but is there any way for me to test the system to find out if I really need this thing or if the Bozo I bought it from installed the resistor just because it came with the old MSD coil? Can I measure the voltage at the coil somehow and tell whether or not the ballast resistor has been "added on" or if it actually needed because the factory wire is missing/bad? I know the CJ I bought has been running for about 20,000 miles with this thing installed, but after seeing some of the PO's other "fabrication" I really doubt that this thing is needed.
Thanks.

[fuzz401]

here are the wiring dwg for a 78 to see in has the res wire


http://img.photobucket.com/albums/v153/fuzzgremlin/engine.gif
http://img.photobucket.com/albums/v153/fuzzgremlin/image002.gif
http://img.photobucket.com/albums/v153/fuzzgremlin/dash_wiring.gif
http://img.photobucket.com/albums/v153/fuzzgremlin/jeep_dwg_4.jpg
http://img.photobucket.com/albums/v153/fuzzgremlin/wiringlist.jpg
http://img.photobucket.com/albums/v153/fuzzgremlin/wiringassc.jpg

[milocj]

Thanks for the links. That shows basically what I am asking. With the Duraspark system I should have the red resistor wire with a white tracer and no ballast resistor. In my case that wire was lengthened due to the fact that the PO had a one piece front end. In addition to the extra length to reach the coil (I don't know if he shortened the Red/White wire any) he spliced a ballast resistor into this wire. Is it the wire itself that adds the resistance or is there something under the dash or a fusible link type section that adds the resistance? I suspect that the guy added the ballast resistor because it came with the MSD coil that he had installed. It now has an Accel coil because the MSD shook itself apart due to the fact that it was zip tied to a spark plug wire loom.
Can I just measure voltage at the hot side of the coil with the key on and the ballast resistor in and out of the hot wire? What voltage reading should I get?