Ring & Pinion -Yukon Gear 3.73 Question

[thelawdoc]

Gentlemen, one of the last major items for me to become familiar with on my recently acquired '65-'66 C10 250-Powerglide 2spd is the rear end. I was assuming that I had the base differential, i.e., no positraction or limited slip. But today, in going through a box of stuff that came with the truck, I found some receipts. One receipt, dated about 16 months ago, is an invoice for a differential overhaul. It is itemized. My eye caught the following items:

Ring & Pinion - Yukon Gear 3.73; Bearing - Drive Shaft Center Support; Axle, etc., etc.

My question: Isn't this a 'limited slip' or 'positraction' rear end?

The reason I am so curious is that this truck is slated for daily use in northern winters. Therefore, I had intended on trashing my stock rear end and putting in something more suitable for long winter climates, e.g., limited slip. I figure that with studded rear tires or chains, I would manage ok. And I figured that, if I am trashing my rear end then I will also put in a diff that is more suitable for better mpg & low rpm's on the interstate. But if I already have l.s., and the diff has just been overhauled, I will sit with what I have and be a sport for the money spent on gas using the 3.73 on the freeway.

I am attaching a copy of the invoice so that you can see what I am seeing.
Thank you for the help. -Alden