I actually don't think the grease was mentioned in any of the past cars as far as a way of getting a better seal during assembly. This case was just one of those old racer deals that got past down thru the assembly of different cars. The gear diff was around a long time ago, but fall out of favor for a ball diff, up till 2ish years ago, they just started getting popular again, so, the old knowledge begins to come back as well.
I think the red silicone grease should work well.