How about something like this to drop the voltage for the overdrive components? It says it's good for 10 amps continuous, which should be enough to operate the the momentary overdrive components. I make a device that runs a 12 volt negative ground tachometer on 6 volts positive ground, so I have some experience with solid-state voltage converters and have found them to be reliable. The price ain't bad, either.
https://www.amazon.com/Electric-12-V...oltage+reducer