David,

I use Valvoline MaxLife. Others swear by ZF Lifeguard 6 and ZF Lifeguard 8. For what it's worth, the Valvoline MaxLife works great for me. They (Valvoline) list it as being compatible. An updated compatibility list from Valvoline lists the 6HP and 8HP trans. Here is the fluid:
https://www.walmart.com/ip/Valvoline...allon/15125768

IMPORTANT!!! For the pan/filter, definitely use the ZF one. I bought an aftermarket one and the filter neck/o-ring was manufactured too small. This caused erratic shifting on turns as the fluid sloshed away from the valve body's intake. I wrote a recent thread on this. Here is the ZF one:

https://www.pelicanparts.com/catalog..._pg2.htm#item4