so my DS module died and i have an HEI module that is good laying around so i rigged it up as so and the module is getting 12V but my 67 mustang which i am sure has a resistor wire for the coil. so my question is can i run the resistor wire to the coil still and get a decent spark the only reason i ask is because i have the original coil in it and i don't want to ruin it

 

I would leave it as is with the ballast resistor/wire in the circuit. You will get the same spark as before as you have the same coil, just a different way to open the primary to produce the spark. Keeping the resistor will also help the 4 pin module to run cooler. It might get hot if you install it inside the old DS box with no airflow.

I just did my installation last week and I found I did not need the diode and the white wire, as my red wire had 12v on both run and start positions on the key switch. I also left the stock ballast wire as it still provided 11.5-12 volt on the coil +. I used a new DS2 vacuum advance distributor with my stock Square style coil with a 4 pin GM HEI module. I did not care if my truck looked stock and did the change because I removed the engine computer.

It seems like a lot of extra effort just to use a 4 pin GM HEI module to trip the coil. The DS2 modules are $9 at my local junk yard. I would have just replaced the DS2 module.

The reason I used the GM HEI 4 pin module was I wanted to keep my stock coil as it was better than the old style round DS2 coils. My stock tack still works fine. And the truck starts much faster then before, with just a bump of the key switch.

Here is a good link.
Dirt cheap Ignition

 

From the article in the above link;"Because of the dwell control and current limiting circuits of the HEI you can use just about any coil you want, including the TFI coil, and no ballast resistor is needed. ".

One feature the duraspark II system has that the HEI does not, is spark timing retard during cranking. This is a nice feature that takes some load off the starter and the battery during hot weather.

 

Great link, JimsRebel.

I've been trying to work out a few bugs with the old Duraspark II ignition in my Ranger and this looks like a good alternative if I'm not able to make the DS work properly.