TreeSeeker - I wouldn't get wrapped around five versus four pin ICMs.
Five pin ICM is the original variant, back in the early to mid seventies. Mopar then went to the four pin variant and used that for a much, much longer period of production.
So, four pin ICMs are more common and more readily available. Five pin replacements are relatively rare, due to a far smaller demand. They may also be more expensive, due to economy of scale.
There's also reason to believe Mopar made internal improvements when they went from five to four pin versions.
Changing over is easy, based on the volume of literature and guidance, as well as the apparently large number of people who have done so.
One route is to also change to the two-connector ballast resistor. That involves simply snipping off the fifth wire at the ICM connector.
Identifying which wire to cut is straight forward, using any of the many consistent diagrams on the web. (I posted a link to a pdf having one such diagram.)
The other route is to stay with the four-connector ballast resistor. In that case, the fifth wire is tied to one of the other wires. (Again, which ones to tie together is clearly diagrammed in multiple places on the web.) I'd probably just cut off the fifth wire at the ICM and jumper across terminals on the ballast resistor.
So, you're probably going to spend more time (days versus minutes) finding a five pin ballast resistor. I'd also bet what appears to be a five pin, in the sales literature, actually turns out to be a four pin. (In other words, they may be using an old five pin image to sell a four pin ICM.)
In any case, I'm done ... do whatever you think is best for you.
