From the earlier thread linked by sstock and even the discussion here, I am still wondering about the presence/absence of a rear transmission cross member in a '53 3100 with SM420.
I did find the crossmember in the Factory Assembly Manual (section 7, sheet 3.05) for Automatic Transmission.
My truck had a 216 with the SM420 and torque tube. Front and rear engine mounts. There was no crossmember at the rear of the transmission.
All my agriculture mechanic experience tells me there should be something supporting the rear of the transmission.
Also, the question of a one piece open driveshaft VS a two piece with a carrier bearing. The driveline shop I do business with tells me they can build either, whichever I want.
