I researched the old 600W awhile ago, Ford called it 600W back in the model A days, I think it was made by Standard (Mobile oil) but it was a brand name, not actually 600 weight gear oil. I was led to LUBRIPLATE Lubricants Company, their SPO series gear oils are the best you can get to match the older gear sets. Their 600W (SPO 299) I think,is actually 250 weight, I put it in my rear end, transmission, & steering boxes. No leakage! Use JD cornhead grease for your U joint, it's 0 (zero) weight.