This unit says it will accept #3 gauge wire. I have not taken a very close look at it. IF you can determine the gauge of your wires and IF you can find a spot to access them perhaps something like this would work. Otherwise, you are looking at male and female 50A connectors, some cable and a box to house it all. Alternatively you will need current rings etc..
https://www.ekmmetering.com/basic-kw...ekm-25ids.html I was very close to installing one on our boat because they get 85 cents a kwh in the Bahamas.