You can also buy the Zinc addative on its own, or run Royal Purple which has the ZDDP in it. I used to drive a british car and had to use oil with zinc just to keep it running lol !
im going with a Big block in mine so it was good to see how your engine sat in there and everything.
but one big question.
Why did you reuse the BMW diff instead of putting a solid axle under the back?
for mine im going to do a Dana 60 shortened for a mini-tub. I dont trust the BMW half shafts with my horses lol