for example -- there is an alarm in the panel for high temp/low pressure, and there are senders that feed both the idiot lights and a gauge, and there are different sensors thread sizes and ohm ranges. I don't mind sacrificing idiot lights if replacing with a gauge, but I don't want to disable the alarm.

What I buy must be compatible with what I have so it requires research if I don't go with Volvo Penta part numbers. That green paint is expensive. ;)