Yeah, check and make sure you have a 19-spline unit, and not a 30-spline.
I had a Dana in my '62 Chevy Suburban, and it was 30-spline. It broke because all six plug welds failed on one of the axle tubes, where it presses into the cast housing. This allowed the tube to get real sloppy, which all came to bear on the last 1/2-inch of axle splines it entered the limited slip spider gears. The result was a spun bearing in the housing (junking the housing), a stripped spider gear (REAL expensive to replace) and stripped axle splines.
After hunting around a whole bunch, I located another Dana 44 out of a '60-'62 GMC that was a direct bolt-in for my Suburban. It too has 30 splines. I bought a new limited slip unit off ebay, from a Jeep. The Dana 44 is the single most common rear end EVER.
Also, make sure yours really is a Dana 44, and not the truck 12-bolt that was issued in '63. Dana 44 has 10-bolts on the rear cover. The '63-'66 12 bolts I looked at were all 19-spline.
-Brad
