Spent some time under my 1941 Chevy GI dumper. The PTO on this rig is made By Central Fibre (which is oddly enough made in CHELSEA, MI). The model number is a simple 2-B. The transmission is the standard non-sycromesh 4 speed as used on 1937-47 trucks.
Please send me some more PTO brand/model #/transmission applications that you have on your trucks.