Finally had time to follow up on this thread.
This is the bottom of the flip head mechanism, that fits on the top of the Y ram on a 6300rpm FP4NC. The head is mounted on a hinged, flat plate that slides on top of this surface, guided by the rollers in the photo. The hole you see here is the access port through which the shift mechanism enages the transmission.

Broken part on the left,
The new part was completely machined from billet, as opposed to the press fit stud into the hole that broke in the original, a weak design. It's possible this was done on purpose so this part would break when the flip head feature was abused, instead of the transmission breaking....
Note the 2 extra holes around the perimeter- threaded for jacking screws- for removal. A nice touch by the Green Baron, considering the new part is a light press fit into the machine.

Shift mechanism installed, and a side view- hard to tell from the photo, but the round peg at the top is connected to the arm that protrudes from the bottom- this moves the transmission gear front to back, engaging/disengaging the drive to the vertical spindle. The slot at the bottom of the arm rides the top of the gears you can see in photos 2 and 3.

Underside of the flip head panel (detached from the flip head- note the hinge pins on the left), that slides on top of the ram.
The horseshoe shaped piece on the right is the shift track- this is what engages the round button on top of the shift mechanism.

Detail of the shift track- normally bolted and pinned to the bottom of the flip head panel. When the head is slid forward this track pulls the transmission into engagement so the vertical spindle can work it's magic.

Great photos! I've often wondered what was under the sliding part of the flip head. On mine, you can just barely see there's a mechanism there, but that's it. I guess you got lucky and the broken peg did not fall into the guts, since you don't show broken gears.

Pardon my ignorance, but who's the Green Baron. Nice moniker!

" Green baron " hahahahah , I like it.

Yes, I was very lucky, no broken parts inside, good design on Deckel's part.

It was a major headache trying to get the slide off- the "peg" and broken part were hanging up inbetween the bottom of the flip head panel and the top of the shift mechanism. You can't just lift the whole panel because it's held captive by the rollers- note the replacable, hardened tracks. When I finally got it all apart and looked into the transmission, it was glorious- the inside of the machine was spotless and the machining on the gears is beautifull.

Green Baron aka Iceman aka the esteemed AlfaGTA, he did me a huge favor in making the new part, I just could'nt afford a new one.

I would be remiss if I did not publicly thank him and the DeckelDoctor (also esteemed! ) for helping me get this machine working.

Now that we know who is the Green Baron, we need the appropriate music, car and good looking sidekick in tight bodysuit (for sweeping chips). Who's the villain?