front axle service kit

[irridian]

 I acquired a 1984 extra cab with a 2.4 diesel. This truck has never been on the highway. It was used to go down a mine drift pulling an ore cart and diamond drilling gear. It was parked for over 20 years because it was in a cave in and pushed down the front clip which I have now replaced. I want to get the front axle service kit but I have learned that Toyota made a 3/4 ton which I believe this is. It has a GVW of 5080 lbs. and my 1985 Toyota extra cab has a GVW of 4800 lbs. I was wondering if the front service kit bearings can handle a 3/4 ton and even if it is a 3/4 ton? Also there is no lable on the diffs and was wondering how I can tell what gear ratio they are? I live in Yukon Canada we do rock crawling as well as ice crawling here.