I'm not all that familiar with 'white' grease, but the white stuff I've seen is a lubricant. Seems to me you don't want to lubricate surfaces that aren't allowed to move unless its absolutely NOT possible for them to move.

In the case of that tapered brake drum fitting...you don't want it to budge. And it can. I've had several 122s that had a mysterious clunk when first going into reverse, then back to forward... and it turned out to be the drum slipping, which wiped caused the woodruff key to be hour glass shaped, and flared the key slot in the axle... effectively ruining the axle shaft.

I'd vote absolutely NO on any lubricant on that tapered fit. Clean it as impeccably, put it on as tight as you can, and have the right puller on hand when you need to pull it again. If you wanna keep water out, I suppose you could install the drum completely and tightly, then back the bolt off, smear some grease on the threads, then re-tighten the bolt. But I don't think its necessary. It ain't hard to get the drum off if you have the right tools.

But maybe the "white grease" you mention has properties of which I'm unaware.

-Matt
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-Matt '70 145s, '65 1800s, '66 122s wagon, others inc. '53 XK120 FHC