although questions aren't supposed to be posted in this section , i will try to help you. the number that you need to post is in a square raised pad on the side of the transmission. these numbers you listed are not the number. the pp number is the serial number.
I'm going to guess the "18" of the first number is really a "1B" which would make it a '71. The other number PP833 3409 is the model number of the trans and the date it was built (10,000 day calendar or something like that).