I found this info on the web and thought it might be useful so I've converted it to PDF and you can download it here:

http://users.tpg.com.au/adslljrb/Differentials.pdf

It's 21 pages, 288Kb in Adobe Acrobat PDF format.

It has Diff codes (What diff do I have?), Ring and Pinion ratios for Celicas, Coronas and other Toyotas, Axle Widths, and Crown and Pinion final Gear Ratio Sets for Japanese and US models.

My apologies if this has been posted elsewhere on Toymods. A quick search didn't bring anything up.

Peter