I hope that some other CCC members with the Speed control option ( 1969 ) can help me with this 'mystery part" !
I’ve checked with Ford Motor in Dearborn ( and they’ve referred me back to the dealership ( 
). Obviously for a 50 year old part no help was to be had there. I’ve also asked a few other member on here ( through private messaging ) as to what this component is for - and the hypotheses range from one-way valve to water trap to air filter to vacuum restriction or delay. I’ve gone through the entire MPC ( section 9000 ) and looked through every part applicable to speed control, and nothing remotely like this item comes up. As well, no basic number was referenced to this part in the Jim Osborne reprints ! ( which is unusual for a Ford engineering diagram )
This small ( about the size of an old thread spool - 1 1/4 " long with a diameter of 3/4 " ) plastic component also has two nipples on either end, but they are ‘off-set’, one at the top end and the other nipple is located at the bottom of the opposite end.
I’ve attached a couple of images, one of the actual part ( with the blue stripe vacuum hose attached ) and another image from the Jim Osborne assembly line ( reproduced ) pages showing its location - up near the firewall, and in the line coming from the manifold and leading into the actual speed control regulator itself.
If it was a filter the interior filter medium is long since gone ( sucked into the regulator ? ) - so it is now just a open plastic chamber.
If it was a one-way valve, that doesn’t make sense, as the passages on the inside show no remains of a rubber membrane. Ford would more likely have used C8SZ-13B064-A for this purpose.
It is possibly a water trap, as the internal baffles are staggered, and the placement of the inlet and outlet nipples would prevent a direct flow-through. Moisture from the manifold ( after engine shut down and cooling ) leading to condensation, which would have to be prevented from entering the regulator.
Vacuum restriction or delay - I’m not sure about, as the movement of air / vacuum isn’t impeded or slowed in any way by its design.
So there you have why I’ve gleaned about this part. Does anyone have any thoughts - especially part number or name.
