I used the following Lucas "Red & Tacky" Grease in my new FG 8485 LST diff. It was at Advance Auto for $5 and I have enough to do a hundred diff assemblies (or more)
http://www.fordtractorpart.com/lucas...3997-prd1.html
I also did NOT pack in extra grease. I just covered the bevel gears well before assembly.
Ken