The wiring harness should work, some minor changes may be needed. The engine plug might be different for example.
All electrical parts for a SOHC4 bike will work OK. Mounting the regulator, rectifier, flasher, safety diode/module, and solenoid may be a challenge.
I think the 500/550 use sliprings to power the alternator rotor rather than using the passive induced field rotor on other models, and the sliprings need maintenance plus these rotors do fail.
All the coils look the same but the GL ones are a lower resistance and should not be used for the others. You want 5 Ohm coils, DC resistance should be around 4.5 Ohms.
The starters are model specific because the drive differs, but any 500/550 one should work.
The wiring itself is, in my experience, basically good after 40+ years - unless butchered by some PO. If the harness has rubbed and chafed, check that no wires have their insulation damaged.
I have not seen it yet in Honda harnesses, but some 60s & 70s wires get insulation degradation that weeps a corrosive chemical from the decomposing plasticizer. If you see green slime/goo coming out of a wire end (by a terminal) the wire must be replaced: this chemical corrodes and destroys the copper conductors.
The bullet connectors are susceptible to damage though: if the wire or plastic sleeve is burnt dark brown or black from overheating due to a weakened or corroded connection, probably the connector should be replaced with the wire cut back to clean bright copper. Definitely clean all the male bullets and female ends, and a squeeze with pliers to tighten the females is a good idea. Multi connectors - you can pull each terminal out of the shell (stick a tiny screwdriver in the open end and push in the tiny barb that holds it in the shell) to be cleaned plus squeezed lightly.Some dielectric grease on the terminals will help prevent future corrosion.
