Little confused here.....

[Boonie]

Hi guys, quick question. I have heard that all 2500s came with a turbo 400 transmission. I also heard that RPO M40 was for a turbo 400, and M38 was a turbo 350. I have a 74 K2500 that has a turbo 350. I know its stock, ive known this truck my entire life. With that being said, the RPO in the glovebox is M40. According to an RPO site I looked at, M40 decodes as:
M40: Transmission, Auto 3 Spd, Torque Conv Var 1. What does all that mean? Thanks for your help.

 

[RetroC10Sport]

M40 was apparently the code for all automatics in 1974.

 

[Boonie]

thanks retro. kinda wondered if I had the wrong tranny in it. didn't know how it would have happened, but stranger things and all that