As I understand it the 77-78 750's came with regular clamps instead of the idiot light panel, and they fit the earlier top triples too. For that matter the clamps from my 92 750 Nighthawk (91-03 same) fit my K3 upper triple, and my K3's idiot light panel fits the top triple of the Nghthawk triple too. The clamp bolts are even the same style, size and length. I suspect that the clamps from many hondas of the period and beyond will fit just fine, honda wouldn't redesign a simple part like that for every bike, they'd just go with the age old standard design.
-Alan