I need some more help. new to this and the search button comes up with THOUSANDS of results but after checking thread after thread i can not come up with conclusive results.

I want to do a full fluids swap, Engine oil, (i have the oil filter # ) 3 on the tree transmission fluid, and rear axle/carrier fluids. Where do i find what type of oil to use for each of these and how much of each. I tried to see if i could google a transmission identification of the 3 on the tree. (like if its a th400, turbo 350 trans, c6 trans i know these are not correct) How do i identify it? how do i identify the rear end as well?

also i heard if these trucks are not leaking fluids then something is wrong with it. I'm okay with my truck leaking if it has to leak. its old and i'm okay with that (normally i'm super anal about leaking fluids and spots in the driveway) I would just like to know what fluids to keep in it so that it always has enough fluid in it.