Myself I would have a buddy help me tow it the mile to the muff shop. I've done it both ways & there's enough to be concerned with during breakin with out the roar of open ex adding to the confusion.

I did the first run on the 360 open headers with the 5A. Just used some 3" angled pipe to divert the exhaust off of the floor boards. Drove it about 40 miles like that too on the shake down run. Have a little fun, then go get your exhaust.

I've fired up a few motors open. They tend to sound very healthy, and you can't hear the smaller stuff.
I'd splurge on a couple feet of flex pipe (if needed) and a pair of mufflers.
Guess John and I agree on this one.
If you want the roar, toss the mufflers in the back for the drive over to the muffler shop.
It's important to use all senses on a new motor...