Hi Alan & MMD.  Gulbransen bits are quite common here in Australia,
and I have a black one here that was restored about three years ago and
not used much.  I also have a brown one (Deluxe model) in bits and can
get others from people here if you need one.   They made green, black
and brown coloured ones, same as the stacks.   I think the older ones
had slightly narrower pneumatics.

John Tuttle was quite correct in saying it would be very difficult
to fit anything but a Gulbransen motor.  But, hey, there's piles over
here, so why not get the right bit!

I know it would cost a bit to get shipped from Australia but if you
can't get one in the US you can always get one here!

Bye

Peter Coggins
Blue Mtns
Australia