Carlos,

Here's a pic from the 48-51 manual,
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0707a.htm

Also, since this is your "first experience working on a vehicle",
I would suggest you read the truck shop manual.

Transmission assembly starts here,
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0709.htm


-Tom

1950 Chevy 3100 w/ 1956 235