RPO Codes for Rear End Gearing

[napoleon.hardy]

I have looked around the site but can't seem to find the RPO codes to determine gearing in my truck. I have a 94 GMC K1500 ECSB 6 lug with the 5.7 did those come with more than one gear ratio? It has a limited slip rear end but not sure if it's a 3.73, seems those are the most common in these trucks from what I have seen. Any info would be appreciated.

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[Project400]

GT4 is 3.73
GT5 is 4.10

Not sure about the 3.42

 

[89RCLB]

GU6 should be 3:42's

 

[napoleon.hardy]

from my RPO sticker it looks like I have a GT4 G80.