How long a trip are you planning? You do realize that the cost of the ferry to NL and back will be expensive - possibly $1000 for your size of rig. You 'll want to spend several weeks there - it is a very big island with plenty to see/do.
Note - above poster mentions taking ferry from New Brunswick - it actually leaves from North Sydney, N.S.
Distance from Niagara Falls to Myrtle Beach is approx. 1000 miles (we have done this many times).
I would consider breaking your proposed itinerary down into 2 or possibly 3 separate trips so you can give the different areas the time they deserve. You are being a little unrealistic unless you are full timing and have many months to travel.
