In the movie Doc doesn't bring the car out with the radio. He is actually in it.
The funny part is that the D will not actually be able to open the door if inside. So Doc had to drive in and pull the ramp gate up just to make the dramatic foggy exit for Marty. I guess you could cut out an escape door in the side of the van. You could use it to serve tacos when you are not trailering the car.
I think there are some guys in Nevada that have a Doc van and a D. I think they may be the people that are doing the car show out there that is coming up soon.
Here is a YouTube clip of the first time the Delorean comes out of the van:
https://www.youtube.com/watch?v=pLRk4xG-JCI