I guess my business partner got off with that stuff. I have a few bins of ICs and transistors but no Marantz switches that I could find.

The 2270 was a workhorse. All that ever failed was the power switches and the "intermittant one channel" due to a dirty tape mon switch.
Keep the PA transistors bias set and the amp will play forever. However, given it's age I'd say the power supply caps are getting soft so, it might sound a little weak in the bottom end if so. Still, that unit would make a good preamp.
Nice find for < $20. If it has the optional walnut case it might fetch 10x that to some collector.