Is this an HO52 and what fluid???

[66 lwb cs]

Hi I was thinking this is an HO52 based on what I have seen on here but wanted to be sure as I some posts on net that the 3/4 ton's may also have recieved the HO72 or is that just for the 4X4's also need to know what fluid it should take as it is leaking from front seal and need to replenish oil and find a new seal hopefully and if anyone knows of or has a set of 3:73's, 3:90's or even 4:10's let me know via pm as I would like to replace the 4:56's that are in it for better cruising. Here is a pic thanks for any help.