I'm just making sure, I did do a search and I saw people saying it, but I have no clue when it comes to rear ends. In short, will this 3.42 gear on ebay fit my 92 L03 firebird.
http://cgi.ebay.com/ebaymotors/ws/eB...category=33731
It's only $20

Also, I've heard people say you need to take it easy on the gear for the first 500miles or so, is this true? Do you still have to do this on a used setup?

 

Yes it will fit, except not on your carrier. You have a 2-series carrier, and those gears are 3-series; so you either need a 3-series carrier, or a spacer.

The person who wrote the ad has no clue about the splines. That issue has to do with the axles and the side gears, not the ring and pinion. R&Ps for the 7.5 or 7.625 rears are the all same, 78-2003.

 

used gear set wouldn't require break in period