Hi, Mike -
What do you need to know, exactly ?
As far as I know, the part no. for seat/mudguard carrier is 42270 for late MM with 17" wheels, and is the same part as fitted to late Bullet or Clipper 350.
If you need sizes of any part of this, I can measure up the carrier on my own Bullet 350 for comparison.
On the other hand, if it's fastener details only you require, the four muguard to carrier screws are pt. #10142, which according to my notes are 5/16" x 3/4" x 26 tpi - CYCLE rate (BSC / CEI). Seat bracket to carrier screws are 5/16" x 11/16", also cycle thread.
Have you made any progress with dismantling the forks ?