I reached out to my contact at suburban and they advised me that your water heater has a 3 4 npt national pipe threading and it has 12 threads inch.
Rv water heater anode thread size.
Before you consider re tapping the threads re check to make sure you have the right sized anode rod.
The thread size in these water heaters for the anode is 3 4 inch npt which is a tapered pipe thread.
To use a standard tap may actually remove portions of the existing threads as well as cut new threads something to be avoided in a water heater tank fitting.
What size type anode do i need for my hot water tank.
Plumbonline have put together a comparison table see below to make selecting your anode as simple as possible as in most cases the owner manual for your hot water service does not detail the size.