Just bought a used transmission (GMA5S390RTZ) for my '01 X5 3.0i & am about to get it installed.

Dealer A told me I should use Texaco ETL 8072 B fluid ($18.50 / litre from dealer).

Dealer B says I could get away with Valvoline Dexron 6 full synthethic fluid or Amsoil ATF ($9.75) for vehicles requiring GM Dexron 6.

Can someone pls advise on what way to go? I need to make a decision urgently