It looks like (if this will work which it should...)

Cost of the adapter + new bosch 80006 glow plug would still be cheaper then the bosch 80035 conversion plug... and new plugs would be very easy to come by if need be.

Thoughts?

I will most likely try it... also after the cost of the adapter, new bosch 80006 plugs can be had for $8 each... less then half of the 80035.

There is a Member who did make adapters for himself to allow the the 12mm Glow Plugs to be used in the 18mm Holes. However, he was a machinist and had knowlege and equipment and time wise it would not be worth the Money.
With the Adapter Glow Plugs you need to match the external dimensions of the 18mm Plugs and then match the internal dimensions of the 12mm Glow Plugs (the 12mm Plugs seal on the angled shoulder right behind the tip/heater Element.

I think that this it the thread of that I have in my notes:
Glow Plug Adapter, regular Pencil to fit Filiment type.
http://www.peachparts.com/shopforum/showthread.php?t=282022

If you can also do it go-for-it.

__________________
84 300D, 82 Volvo 244Gl Diesel