The glow plugs on a stock M1009 are 12 volt. They get the same glow plugs as a 1985 Chevy or a 1998 Chevy for that matter.
Delco 9G or 12G is what they came with when new. I would suggest Delco 60G to put in now. The 60 G is self limiting so the chance of swelling or exploding are greatly reduced. However, the tab for the wire is bigger on the 60G than stock. You can trim the wiring tab on each plug or replace the terminal end clip on all of the green wires. Either way, the 60G will require a bit of work the first time you install them.
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