I have some good experience with the D3 and I pointed that one out because I think it is the correct one. It says "Automega" which is a name for the D3. Also, a D2 cone won't have a label on it for the focus track. I think they are just 1/4" off in the measurement. The D2 cone is going to be 4 1/2" and not have an indicator for the focus track.

The focus track number on that cone for sale may not be easily crossed referenced to your focus track because some focus tracks had cryptic numbers on them; frequently not the six-digit omega part number. How do you know you have a 135mm focus track. Does it say 135mm? Some are that easy to decode.

You should be able to make a bellows. The bellows only needs to move a small amount. Most of the focusing travel is via the lens cones.