I settled for this:
 

I saw Todd on a Live at Darryl's.
 
Sweet set up he has in Hawaii.  

If it was the 60's, I believe the only thing available was the Univibe. The MXR and the Biphase are from the mid 70's

The Univibe is analyzed here:
 
http://geofex.com/Article_Folders/univibe/univtech.htm
 
Don't forget that the whole mix was sent through something, not just the guitars and instruments.
 
That's why I thought it may have been a conventional tape flange studio technique - but that would not explain the noisey grit, would it?
 
The UniVibe had those CdS photocells which controlled the phasing and they are pretty noisy, I believe. These things are often used in Photocell based optocouplers, feedback isolation, primitive voltage control, and even on compressors. They have a pretty long time constant on the rate of change and work on incandescents very well.
 
This seems like it may have been what was used.