[midniteblues]

Well I talked with the local drive shaft/axle shop guy.
He thinks the engravings are just gear set up scribes. Kinda figured that.

Tearing down this dana it seemed like someone was in this before.
My spid doesn't list any optional gear ratio. From what I read here on the board is my truck should have the standard 4:10 ratio.not the 4:56 ratio. All the date codes seem too match my truck though. Seems weird but I guess the gears were changed. Perhaps they were done when the dump bed was installed along with the heavier leaf springs.

But anyway I picked up some different oil seals.
Here is a pick of Timken and Spicer oil seals.
The oil seal in my pic above is a national brand seal.
National oil seals local mom pop store $18. A peice.
Spicer seals from the axle shop $11. Each
The orange seal is a Timken seal from auto zone $8. Each,these were listed as a duralast part.

I didn't try napa. These are all part # 5131.

Just figured I would put this out there since I could.
An if you ask me the Timken seems too be the best out of the three. And the fella at the shop said all these seals are designed too eliminate the oe steel guide in the axle tube.
Also the front axle gear is a 4:55 and the rear is a 4:56 he said it's common thing and doesn't matter.