The stock rectifier is a solid state piece (no moving parts) so as long as yours is working, there isn't much to be gained / improved by replacing it. The benefits of regulator replacement have been argued a good bit on this site. I am quite happy with the solid state regulator that I purchased from Oregon Motorcycle Parts. It has been in use for over 3 years and as he states on his site (at least for the 750s) it actually charges at idle with over 13 volts at the battery. My stock reg never quite managed this. I even have an electronic ignition, 3ohm coils and halogen headlight drawing additional power, although running lights are LED units. . . If you are looking to consoladate the parts into one piece for convenience or aesthetics then the combo units might be of interest. If your rectifier is fried then a combo unit might be of interest. The cost of separate pieces from OMP probably isn't much different than the cost of a good combo unit however, and the parts fit in the stock locations. . .Making sure that all the wiring is solid and connections are clean is probably one of the most import "upgrades" you can do on these old bikes. Damaged wires and resistance from corrosion will suck up a lot of alternator output and can ruin your nice new electronics, so consider a wiring tuneup as part of the deal. Pay attention to the fuse box in particular . . . . .