Splits through '66 were single circuit, the '67 was dual circuit.  A dual circuit MC can be fitted without too much trouble.

FWIW my Split is a '61 Standard, 6v 40hp 1192cc motor, single circuit brakes.  It's slow, the brakes are not the best and the handling is below average in comparison to my other VWs.  However I enjoy it and do not see these as drawbacks, they are part of the personality.  I can cruise at 55 mph, it will go faster but I don't.  Hills are challenging and it does not go on interstates.  I don't know if it is underpowered, I personally would not want much power in a split window, something tells me they were not designed to go very fast.

Dave
251.org
87 Vanagon
61 Microbus
88 GTI 

>Question: are those single circuit brakes or dual circuit?
>
>Just curious. BIG topic of discussion on another list recently.

It would probably be a cinch to fit a Bay (split-circuit)
mastercylinder to a Split. As well as the front beam, with balljoints
& discs.