Congrats on snagging the OD tranny. You are correct, the non syncro reverse/1st is pre early 60's. It is also identified by the 4 bolts for the shifting fork side cover. The 7 bolt versions have the rev/1st syncro, at least that is my understanding.
The O/D section doesn't use a shifter to engage it. It is engaged electrically by the solenoid on the left hand side. The governor on the right hand side controls when it kicks in speed wise (@25-30 mph).
The small lever aft of the solenoid is the lock out, as in it locks out the activation of the O/D altogether.
There is a good article about these O/D's here:
http://www.fordification.com/tech/overdrive.htmAnd a good thread on this forum:
http://www.67-72chevytrucks.com/vboard/showthread.php?t=313886I'm also a few weeks from installing mine. My O/D is also an early version like yours. Another thing to note, the holes in the ears that bolt to the bell housing. Are they thru holes or are they tapped? The thru holes (so I've been told) indicate the trans was originally from a car. I plan on using a nut and bolt on the bottom two holes.
What are you changing in the diff? Ring and pinion I assume.
Going from what ratio to what ratio?
