Hi J.B.,
I enjoyed reading your AA story. Too bad the express bed was scrapped, they are very rare. Yes, my truck has the 2 speed gear box behind the three speed transmission. It also has the Ford "flat disk" wheels that were only made in 1929. They were discontinued because in late '29 Ford offered the 4 speed AA truck with dual rear wheels. That's when Budd Company started making rims for Ford trucks, a tradition that continues today.
My truck came from a farm in Emporia Kansas. It spent the last 60 years there after being used by a fellow who ran a delivery company. I don't think it was ever owned by a railroad although it probably delivered express parcels around town that came in by train. I have driven gravel trucks and fire engines but the AA Express is one of the hardest trucks to drive. With 16 spring ply in the back (if there's no load) you feel every high spot in the road.
Stewart