ZJs were also low pinion, IIRC.I would just rebuild the one you just bought. You'll need a bearing, a seal, a crush sleeve, and a pinion nut. If that doesn't work out, you can always buy another axle later, but you already know that 3.73 isn't a common gear ratio.
That's correct. Low pinion.
Remember LP 30s where used in wranglers too!