Converting single-axel to tandem

I’d like to have some recommendations on someone who does good/reasonablly priced trailer work. Any help would be appreciated.

The Trailer Shop in Mt. Pleasant. I believe thats the name. They are off Coleman Blvd on Meeting Street I think. They have done work for me and see to be reasonable and quick.

R.D.S. IV
21’ SeaPro CC
150 2-stroke