FWIW, I have a 1978 300D which had series loop plugs, and now has pencil parallel ones. Best thing you can ever do...

Re: the stock loop style controller, yes it will work the glow plugs, but it will not turn them off until you start cranking- the light stays on indefinitely - something people not familiar with your car will need mentioning of the fact. I just count to 10 or whatever. Looking at going the push button way myself eventually.

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1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD