I might be pickin' up another Tracker, an 89 with a VIN that starts with "J". This is a Jap car, right? And according to some searches, it could have a 1.3 with 5.62 diffs, right? Which letter (or #) will tell me if this is one to covet?

Yes, it is a Japan made vehicle.  If it is a tracker, then it will not have a carbed 1.3 with the 5.62s.  The only carbed 1.3s I have seen have been in suzukis.
If it has a carbed 1.3 engine and a manual tranny, then it should have 5.62s.
Just get the complete VIN, run it in a free online VIN decoder and it should tell you what engine it has.
From what I have found, you have a 4% chance it has 5.62s.

Aw man Tone, if it's one of the 1.3's what a find!

Well according to 5 different free VIN sites, It's got a 1.6 MPI.  I think I'm still gonna jack it up and spin and count. I've always jacked up the whole rear and spun the wheels one turn while counting the drive shaft revs. Seems I've read that you can jack up one side, spin the wheel two revs while counting the shaft's revs. True? Wish me luck!

Well according to 5 different free VIN sites, It's got a 1.6 MPI.  I think I'm still gonna jack it up and spin and count. I've always jacked up the whole rear and spun the wheels one turn while counting the drive shaft revs. Seems I've read that you can jack up one side, spin the wheel two revs while counting the shaft's revs. True? Wish me luck!

Yep.  2 turns of the tire, count the driveshaft revs, that will tell you the axle ratio.
1.6 will not have 5.62s....but you can check anyway.

Thanx, cuz.   Not like I need another Tracker anyway, I have about 4. Would be cool tho to be able up the ratio. On the street with 33's, it takes forever to wind up to 5 g's! Any body else interested in a $600 Tracker, lemme know. If I don't get it I'll pass it on. It's in Detroit.