Military Vehicle Repair: M1009 glow plugs, glow plugs, glow plug

Question
Are the original glow plugs from 1984 (-20 P) still good for installation. I had 6 NOS glow plugs and 2 'NAPA' plugs  installed and the NOS plugs overheated and went bad (swollen) very quikly.....the NAPA 13 G were fine. Are there a top of the line, modern glow plugs available  ?? And lastly, what is the voltage coming out of the resistor bar----and at the glow plug itself ?  

Answer
13G is what you want.
After the relay closes, the voltage will be 12 volts, but if you just measure it while the truck is just sitting there, it will show 24 volts.
It is a resistor, and when a load...the glow plugs...is put on it, it will show 12.

Van