Slick 60's

Hey all! Im pulling my hair out trying to find this information!! Ive done all the searches and looked in many catalogs but, still no answer. I have a 66 f100 custom cab, long bed, 352 FE, CruiseOmatic 3 speed. I just need to know what the rear end is. Luckilly (I thought) I still have the ID tag on the axle. the numbers are as follows:

WDM-H
3 25 6FA 3B

There is also a 42 DIF and 12 DIF formed into the front of the differential.

can anyone point me into the right direction??? Thanks!

Big bearing Ford 9"

Should have 3.25 gears.

28 spline axles. Open differential.

For future reference:

http://www.fordification.com/tech/rearends_ford04.htm

Thanks Dirky!! I really apreciate your reply!! im still a newbie with my truck. Im trying to read everything i can to get educated. Thanks again!!