I apologize to the electrical engineers because I always get it messed up volt vs amp, but if its a 400 amp tesla charger, and you install a 350 amp new charger, its not something you can tweak in the field. unless there is some specific adapter, which is expensive and incredibly long lead time. These aren't going to 120/240v systems. its the same reason the electrician who comes to your house to wire an LED light isn't the same guy working on the transmission lines. orders of magnitude difference between this and what you have in your house.
if the volt/amp requirement is different its a big deal. like ripping out all the wiring to at least the panel with the switches, if not further than that. we run into this all the time with elevators. We specify and design to one elevator manufacturer, contractor goes out and buys a different elevator, and has to rewire the whole system. same thing with mechanical units and most heavy equipment that is hardwired in.
its not like a hose, where you physically adjust the opening to be bigger or smaller depending on how much you want.
if the new one is the same volt/amp, its not an issue. but color me sceptical.