3.25 ratio. 3cb could be 1963 C = March B = second week. Just a guess here. Take a picture of the tag and post it up.
Too bad it's not 3L25, the L means "Traction-lok", but I don't know if they had 'em in 8" in '63. It looks like you already have a Comet, presumably with the small weak six cylinder rear end. You can just measure its width and compare to the suspect diffy. I'd take off a wheel so you can get the wheel mounting face of the drum distance, since the 6cyl brake stuff might be thinner.
Measure the width. It is one, if not the narrowest 5-lug 8-inch rear ends. It should measure out to 56-inches, from drum face to drum face. Early Falcon/Comet rear leaf springs were narrower than those in the Mustang. The spring perches should reflect that narrower width. Those perches should also match the spacing of the early Falcon/Comet. The Mustang has a wider tub, so those perches are spaced wider.
The top line (look at it again) is WCS-B 2. That is a rear used in a 1963 Falcon, 7-3/4" Ring Gear (8"), 28 spline, damper type flange. The second line is 3.25 ratio, built on March 8th 1963, plant code 521. It is what the seller claims.
My question is the seller asking a 'rare' price for it? While not a particularly common axle, Ford did build a fair number of Sprints and the V8 was also available in the Futura line so that axle wasn't exclusive to just the Sprint, plus don't forget the same axle was also used in the V8 Comet. Other than the width, there's nothing unique about it compared to other 8" rears. Plus the early versions ('62-64-ish) had a known issue with too-small pinion gear bearings failing which Ford addressed in the later ones by fitting slightly larger bearings. It is possible to upgrade the early rears to the larger bearings but that will require a rebuild to do so.
what would be a fair price for this rear? Comes with springs and drums too. "removed from a moving car"
I paid 500 bucks for one out of a Maverick - drum to drum with the e brake cables. It had the later HD third member. That seems to be the low end asking rate for ones from Falcon's and Mustangs. Maverick' are a bit narrower at 56.25 WMS to WMS and aren't as common, at least when I was in the market. The local Craigslist has several ranging from $450.00 to $850.00. Don't know if they are selling or not.
If that’s the price of admission these days, the 8.8 Explorer, complete with 31 spline axles, traction lock, and maybe even disc brakes, if you’re so inclined, begins to look attractive.