I think mixing different brands or part numbers affects how ALL the glow plugs work..
I had no choice but to put in 2 autolite used ones I had from a parts 6.2 with a busted crank,and ever since I did,I have either had starting troubles or it simply WONT start when its below 30 degrees or so..I have been forced to use starting fluid twice,to plow my driveway..(now the truck wont move,I think the rear end is F*****,but thats another post altogether!)..
I read somewhere the different types of glow plugs draw different amps,or have different resistance,and as a result can reduce the current going to the other glow plugs..(also I wonder if having a "dead" glow plug or more than one afftects how the others work?),,,but I had 7 out of 8 put in new in my trucjk back in '03 when I got it,and left the one I cant get all the way out in it with the wire hanging off it and it always started fine till recently--when I discovered 3 of the AC 60Gs were not only not working,salt had eaten them away SO badly the "hex" on them was about 1/4",I had to hammer on a 6 point 8MM socket on them to get them out,and was lucky they DID come out!..
I couldn't belive how rotted they were for only being 5 years old--while the autolites from my parts engine looked brand new,and I know they were in that motor for years..shortly after I put the 2 autolites in,is when I the engine had it's "horrible clattering noise" spell..might be coincidence--but I'm praying one didn't swell up or drop into the cylinder!..seeing they aren't "rated" for a manual push button glow plug switch like I have,I'm hoping they didn't burn up or expand ..