Will depend on your uses for the trailer other than
to just haul the car. On any trailer I would advise
getting a awning... one of the best things you can
get for it(shade is a valuable commodity at the track).
I store my car in it all the time unless I'm working
on it. On one of mine I made fold up bunk beds that
hinged off the walls... if you plan on sleeping in
it. All of the fancy cabinets they sell for them look
nice but you can put your own in for a lot less $$.
I would suggest at least 2' longer than you think
you need and the big axles are a must(with the 16"
wheels)