[DeTomaso] oil , zinc , ZF gear oil

[boyd casey]

I went to my local auto parts store to buy 90 wt gear oil for the zf and
They only had multi weights 85- 145 and others no straight 90 weight. So do
I need to stick to the manual and get straight 90wt? also  They didn't have
any zinc additives for motor oil. What is the recommended weight and brand
oil for running a slightly modified 351 Cleveland engine and how much zinc
additive  and what brand should i use ( look for. )Boyd