Truck tranny?

I'll have to play dumb on that one! Its been 4 years since I've been in the rig.
My best guess would be a 4 speed, but it could be 5 if it has a compound granny.
I am not aware of any automatics for 6 x 6's in the early 70's. Many of the early 50's models had a 6 speed automatic ( 3 high/ 3 low , but those were coupled to higher RPM gasoline engines.
I do remember that it required a lower gear to hold the rig on the Cumbres/Lobato downgrade, but I can't recall if it was 2nd or 3rd.
This truck is in exceptional shape. If memory serves me correctly it came from Los Alamos with real low milage. I think Soni did a piston/sleeve
transplant the night before it went into service, but otherwise you just don't find them in any better shape.