The idea is simple. The details can be many and are up to you to work out.

Don't put on the tricycle gear. Buy an appropriately tall and wide main gear. Position it so that the wheels' axles will line up with the leading edge of the wing or very slightly forward. Mark the fuselage so that you can bolt the gear on the fuselage where all that lines up. Go inside the fuselage where those marks are and place a plywood doubler on the floor of the fuselage to support the main gear and take the bolts. Epoxy in that doubler. Now put fuselage side douplers above that floor doubler so that the fuselage sides will also take the landing stresses.

Get yourself one of the tailwheel assemblys the LHS sell, and put it on the airplane. It'll connect to the rudder most probably.