The 13/44 is the tooth count, 13 teeth on the pinion gear and 44 on the ring gear. That divides out to be a 3.38:1 ratio. Dana/Spicer axles have an oddball-shaped cover plate with several straight lines and angles involved, so the oval shape of the one in the picture eliminates Spicer as a possibility. There's usually a stamped ID code on the top of the passenger's side axle tube, but sometimes it takes some vigorous wire brush and flashlight work to find it. If there's an older salvage yard in your area that still has a copy of the Hollander parts interchange manual, that book can provide a wealth of good information.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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