You're right about most of those switches, Andy: they are the ones used in the CB175/CB350 bikes of the era, but with the connectors fitted for a 750. The contacts get so hot on the IGNITION circuit that the solder melts inside and lets the rivets wipe off, ruining the switch. They are only rated for 8 amps, and the 750 uses 8-11 amps with the headlight on, cooking the switch. I through one, too, so I solved that little problem.
Problem here has been: the 750 version of the switch, with the heavier wires and internal contacts, just isn't available anymore, at least here in the U.S.
So, I guess it's time for another SOHC4 "kit": I've created (but haven't sold one to anyone) a relay add-in and extra backbone wire for the 750 that has solved the problem, in mine. In a nutshell, for those of you who understand the electrics, it takes the IGN black wire from the circuit to turn on a relay, located in the headlight. This relay is connected via an independent 16 AWG size wire, all the way back to the battery, where I use a separate, blade-type fuse, to feed the system away from the switch. Since this larger wire will carry more than 80% of the overall current, the key IGN still functions as fully normal, but it has a parallel boost circuit, much like a power steering system in a car. The relay connects this extra power wire back into the BLACK circuit up front, dropping the loads from the keyswitch.
Then the key only carries about 2 amps, and the switch will last a very long time!
For those who want to make one yourself, get a 30 amp automotive relay (12vDC type), 3 feet of BLACK wire, 16 AWG is fully large enough, and a blade fuse socket for 20 amp size: install a 10 amp or 15 amp fuse. Wire as described above, and you're in like Flynn.
If anyone wants me to make "kits", let me know, and I'll put a package together, like the Hondaman Ignitions. These might costs around $20.
The smaller SOHC4 bikes don't have this problem, as generally they don't generate much more than about 8 amps to begin with. So, they don't suffer from this quirk.