Enclosed car hauler...

Mine is 24' with v nose. The car fits easily with bonnets to e-track. Believe me the extra room makes it easier to load/unload. You need some space to work in and strap it down. Room for a cargo box to store the straps and such. If you are doing shows then you need room for chairs and an pop up awning. This will allow you to center over the axles for a great tow! JMO.

New Under 5k with 5200lb axles. And yes your Duramax will pull it about 1/2 what my RAM will! Kidding!

You could fit an 18' but damn it would be hard strap it down. I rented a 20' to haul the body for resto back and forth and it was just enough to have room to bend down and strap. Don't know how young and limber you may be so think ahead if you are going to make a purchase for years!