Also about whether the GL4 or 5 is appropriate. It looks like GL5 was the spec, at least without suregrip.
You could also email Widman. While unlikely to have experience with the DANA rear behind a hemi, the Dana Powerlok (suregrip) was widely used, and he's seen lot and lots of stuff torn down and examined. Being in Bolivia he has nothing to sell. He's just posting info in English to be helpful to the old car community.
