Bill is right, the conversion kit will work for you. the kit was to change the big loop style plugs to the pencil style plugs. For a little while there were pencil style plugs made with the bigger OD.
I think that if you try and connect the existing wire to your existing glowplug set-up it will not heat the plugs long enough. The conversion kit (about $100 off ebay) will give you the plug style that you need and the OD to fit your head along with a bunch of stuff you do not need.
The other option is to take the old plugs, chisel out the inside, and run a tap into them to take the plugs off the newer head - presto, a converter for the newer plugs. -Andy

__________________
andy t
'78 300d
'95 volvo 850, wagon
'86 300sdl - engine out, maybe I'll have it rolling by June

whole bunch o' bicycles