Brackets on the left with the sort of half round stiffeners pressed in are for 68 - 70 soft tops; right brackets are for the 65 - 67.5. There is a "blade" that is mounted to the soft top that slips into these. The bracket mounts just rear of the door opening on each side.
Paul
68 SRL311-05416
68 SRL311-03507 (currently undergoing restoration) 67.5 SPL311-12278 - big parts off to scrap, small stuff in buckets www.datsun-roadster-parts.com