Just checked the Bristol parts list
Resources - Bristol Cars - Owners and Enthusiasts Forum
and the 409 & 410 used the 64032175/6 front calipers, so it 's reasonable to assume that it was the 411/412 that used the 64032280/1 front calipers which were common to the Jensen (presumably Interceptor).
I have no idea what the 603 used. Anyone got a parts list for the 603?