SL;
C1800 has it right...changeover from earlier
hydraulically activated (located at hyd brake distribution block on firewall behind engine) to later
mechanically activated (located in pedal box of footwell) BLSW took place in 66-67' (market dependent).
I have been on a campaign to get owners with hyd type to change over to the later type for reliability and other advantages, since I recognized the safety disadvantages of the hyd switches years ago. See:
http://www.sw-em.com/safety_bulletin_4.htm
Further suggested reading:
http://www.sw-em.com/hydraulic%20bra...es%20notes.htm
Cheers