They keep the 4.88 and 5.12 ratios in stock. You will need to modify these ratios for installation in your diff housing, as these are shorter than the OEM gears. You can contact Mike Van Steenburg at ISC to have this service performed, 863-324-2742. He is located in Florida.
I believe that you can also order the 4.30 gear from the GTUs model from places like Racing Beat and Mazdatrix. However, the 2nd gen. cars don't race very well w/o the 4.88 or 5.12.
Good luck.
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Chris Wire
Team Wire Racing
ITS Mazda RX7 #35
[This message has been edited by Chris Wire (edited March 27, 2002).]