Stanger,
I used a synthetic grease, CV-2, though I later discovered that For made a specific grease for the application. I thought about cleaning out the box and repacking it the Ford box grease but have not experienced any problems with the lube I used. The CV-2 goes for $10 a tub while a good Hi-temp moly should run 2 to 4 a tub. I never checked with the Ford dealer regarding the price of their box grease.
Hope this helps,
Pat