I visited Randy's Ring & Pinion in Everett, Washington about 10 days ago. During my visit, they rebuilt a GM 9-1/2" six-lug axle I brought with me using new 3.42 gears, an Eaton Posi and all new bearings/seals. A new article about Randy's and rear diff setup will appear here before long.
After running the truck for about 1500 miles since mid May, I've decided to stay with 3.42 gears. It's a lot of fun on the highway with this gearing, and 1/4-mile performance should be as good as or better than 3.73.
Thus far, the truck has run a 13.9/109 in 2WD and 13.7/107 in 4WD according to a G-Tech. This is when run in Tow/Haul mode and with the Attitude set on level-5 with the EGT limiter disabled. I also have the "defuel on locked shifts" set to off. So far, no trans issues. I think there's room for improvement...
Coming soon will be an NOS system, a Predator programmer and a Banks wastegate actuator. The combination of these items plus the Juice/Attitude already installed should allow the truck to produce some interesting numbers.
MP