I'm almost ready for 3.73s in my 93 6spd. Before I start, I want to have everything to fix my speedometer. I know the powerprogramers correct the 94&up, but what do 93's use? Thanks

 

I believe you're right, the 93's need to have the speedometer gear physically changed out, instead of reprogramming the PCM. Not sure of where to get this though, sorry.

 

It depends on whether your car has a 700R4 or an M6 tranny. If it has a 700R4 then there is a little plastic speedo gear that get replaced in the tranny. If it is an M6 then SLP sells a speedo calibrator.

 

There's a guy, or rather a company, on ebay who has been having a lot of "brand new unopened" SLP speedo recalibration boxes for sale. Saw the last one go for $71 and change. Not bad. So I emailed them, through the ask seller a question link. I asked if he had many of them, and if he would be willing to sell me two of the outside of auction.
Earlier I today sent him a paypal for $148 shipped for two brand new units!!!

On ebay, his ID is horsepower1, and they've got a website too, www.foundadeal.com.

I got the boxes today, and both were factory sealed!!! I opened one up, pretty simple, PITA to install though. You can only correct to 3.42, 3.73, or 4.10, but it's better than nothing.

Give them a shout if you need one!!

I copied this post off of http://www.speeddensity.org/
hope this helps