1966 dual master cylinder

here. rock auto for $23

CARDONE SELECT Part # 131323 New CARDONE Select Master Cylinder

http://cardone.com/English/club/members/customer/ecat_brands/imageinfo.asp?PARTNUM=13-1323


not sure you even need a proportional valve with the drum brakes. most guys i know run the front brake line from the master cyl. to a tee then to each wheel..