I was looking at a Motown anthology 2cd definitive compi thing by them last week. They seemed to be one of the most intense bands on the label around '65. Very gospel influenced and I think that was around the time Hendrix passed through at least their touring band.
Think I might grab that now.
There was also a 5cd set of their T-Neck material that came out some years back. Covered the era where they were covering hippy tracks and getting pretty funky at the same time.
Must listen through that.
Stevo
EDIT
God, only just realised that the 2nd of those is the set you're talking about. Hadn't realised it went up to 3+3 for some reason.