Someone is selling a Military 24 volt glow plug controller on ebay (280216398367) and indicating it will work on all 82-84 GM 6.2 diesels.

Of course if someone knows how to make a 24 volt device work on 12 volts, without spending a lot of $$$, let me know.

why not just upgrade to a manual system - that way it will never fail and leave you stuck somewhere, and it is a lot cheaper. Get a starter solenoid from a ford truck ($20) and a momentary push button switch - on my van the solenoid even mounted right in place of the stock relay (which was still working so i sold it on ebay to cover the cost of the conversion). Very easy to do.
Paul