What is the best option for a surge protector for a RV that requires 50 Amp service?
How many joules is enough protection?

Need to explain where the protector could be installed?

The 50 Amp outlet on a building serving the RV?

The distribution panel in the RV when is is mobile?

As with any surge protector, always get the highest joule rating you can afford.

The installation would be in line with the existing 50 amp cord or could be a type that is installed at the juction where the cord enterd the coach,
The 50 Amp is at the post at any RV park.
The distribution panel is built in the storage bay where the cord enters the coach.

I am looking at a portable unit by Surge Guard 50 Amp that has a 1750 joules,6500 spike protection, 240 volts.
The quesstion is... what is the best value and protection. These units can be expensive.

Sorry for the delay in getting back to you.

The unit you chose is fine.

See some details about installing it in an RV:

Surge Guard 50 amp Installation - iRV2 Forums