A couple of very cheap-to-free CB750's of about that vintage have passed through member's hands over the last two years, Guy had one not too long ago, I think, before the last Goldwing. Remember the big building closest to the driveway at Roys? That's where Roy keeps the stuff that has a higher disassembled value - if he had one, or a set of 4, it would be there. It has become difficult to buy carbs from Roy for less than $50 apiece, lately, though. Maybe NewLife would have units at a similar price, or perhaps cheaper?
I have a set of mid-70's Honda carbs in a box, but they must be off a 350/4-400F or 500/550-4; they are very small. I will pass the message on to Mike McLintock; he had a CB750 not too long ago, and has that friend in Hooterville with 125 motorcycles or something...