I have manual glow plug operation with AC60's. I find they need more time the original plugs it came with. If the wait light goes out after 7 seconds, I give it another 7. basically double the wait light period. Fires up quicker this way. This is more than safe as the AC60's take 20 seconds to get to the maximum temperature of 1850 F. I also after glow, say 7 seconds after start up. If its really cold I'll wait 10 seconds and give it a second after glow of 7 seconds.
Of course if you have the original plugs; AC-9 or AC-11, I think AC-13 was even used, disregard this. They are 6 volt plugs that are supposed to be fast heating so they will only need what the wait light shows. Frankly I'm surprised anyone is still running these as they have been obsolete for many years. They burn out easily and swell.
How it is that you can buy a CUCV and still have these plugs reminds me of the scvmbag low-life I once called a friend. When I first got my CUCV the plugs burned out the first month when the key was left on while working on the truck. As I knew very little diesel-wise back then, asked if he could get me plugs. Sure, $220.00. Get it on the road, 3 months later, hard starting issues start. Begin reading SteelSoldiers, test plugs..4 are no good. Go to parts store, couldn't get originals if I wanted, AC60g's had replaced them. Take the old plugs out. He had put in a bunch of used AC-11's that he had lying around and pocketed my $220.