Mick,
Bully's had double pinch bolts on the bottom triple from about the Mk3 Pursang 1968(possibly earlier) and the tops had double pinch bolts from the Mk5 Pursang.All Alpina's and Sherpa's from about 72 had double bolts on the bottom and later on the top too.
I think the triples that Mainline has will have no threads for the pinch bolts,they will be through holes for use with a 6mm bolt and nut.