I was installing a propane tank and hooking up my Truma Combi water heater/heater and stove. I figure the step was to install a propane detector. I am installing their combo CO unit , but they have just a propane unit available. Normally I wouldn't think much about posting about this , but I was surprised by the adapter plates that come with the unit. This unit is thin and basically flush mount. The various adapters should cover the hole your original unit had. The replacement date is right on the front of the unit also.
RVsafe COand Propane