Thank you 81GSL12A... I just started a thread about how no one got to the point with this topic and you made it cut and dry. Great Job! Will start my hunt this week.

Ok i only have two questions.
1) It says you need a rearend from an 83.5-85 with bigger axles. But on page 2 of this thread, a guy asked if it will wrk in his '83 and someone said yes. i have an '83 GSL, will it work without swapping the entire rearend?

2) I may have overlooked it but I havent seen a sure answer. Do you use the front or rear from the kia?

83 was an odd year fo the 7s. It was a year where some parts/upgrades changed in md-year and the the differential was one of those parts. To make it simple take a look at the driveshaft flange that bots to the diff, If it has through bolts and nuts holding it together, then you have the big axles that were carried over to the S3 model. If it has bolts only and no nuts, then you have the earler version with the smaller axles.

You use the front R&P from the Kia,

Can I swap the gears from a Kia into my small axle '81 diff? I'd really rather not replace my entire rear end assembly (again) if I don't have to, but I'd really like the short gears for Solo II.

I'll have to check. I believe my car was built 4/83 if it helps any. If I do have the smaller axles, does that mean i have to swap the entire rearend and driveshaft?

Also, still wondering about if you need the front or rear diff or it just doesn't matter. Also, is it the same for 4x2 and 4x4?

how about a 4.7:7 rear end with 225/35/18 tyres?

found this site very useful
http://www.differentials.com/calc.html
it says 4636 rpm?! @70 MPH yes MPH which is the speed limit in the UK