Need some deep tec help, Thank you

When I go to look for a 1966 67 auto trans (I have a couple to look at tomorrow ) what cast numbers am I looking for ?

For instance this trans is for sale and has cast numbers on it, where would I find the reference numbers I need for my 66 170/6 engine ?
I do know I need a 18 spline out put shaft from the info I got from Charrlie_S'es friend.

Here is the for instance you can look at and this will help me tremendously as I hunt one down.

http://www.ebay.com/itm/MOPAR-SLANT...Parts_Accessories&hash=item1c3488a0dc&vxp=mtr

I know I can be a pain but I have looked and looked with out any help before I bothered you all here. Thank you very much :glasses7: Mike..