Tech question K10

[beanious]

Hello all, I have a 1971 K10 shortbed with a SBC 350, TH350 and a NP205. All new. I have less than 5,000 on the entire drivetrain since all three have been replaced or rebuilt. It's lifted 6" suspension and 2" body, as a result I installed custom length driveshafts from Tom Woods (really nice pieces btw). My question to all is what everyone thinks 4WD speeds should be limited to. Obviously it should only be in 4WD on dirt or snow and I should be careful because 4WD doesn't mean 4wStop. I would just like a firm MPH to ensure nothing gets damaged as I travel over Donner Summit CA in the winter months. Thanks for your help!