Hi Ryan
First thing i would do considering the history you provided...
Order an new PMD and get an extension harness and heat sink from a reputable source and install,lots of ideas for new locations on this site.Do some reading and pick your location.If you keep the truck you will need a PMD at some point so it's a good place to start.
I would get the new Stanadyne grey PMD,but there are some other ones out there.I didn't have much luck with the others.But some people swear by them.
The test for a PMD is to remove it and find a lake,toss it into the lake,if it floats it's good if it sinks leave it there.
The ignition switch is another place to look for problems.
Thomas
90 Chev 3500 c/c 4x4,6.2na,400 auto,4:10 gears.DSG Timing gears,main girdle, isspro tach, pyro,boost,oil and trany temp.Dual Tstats, High volume peninsular pump,on shelf, Custom turbo and intercooler 85%complete. Change of plans for the dually, it's going to get a Cummins. Both trucks are Blue 90 4x4 crews