Anybody can camp in the North 40 (spam can) parking area. Homebuilt,
classic or otherwise. You often see people who would qualify for
showplane camping parked up there for the exact reason you have.

It used to be that homebuilts could park in with the classics, but
since the homebuilts got their own camping area there seems to be
some rift between the two communities. Never hurts to ask once
you get there, but be prepared to deal with the least common denominator.

The North 40 isn't that bad. I parked there two years. There's
no blasted PA system and your much closer to the off-field services
(Restaurants, groceries).

Do they have showers/bathrooms in that North 40 parking area just like
in homebuilt camping? I haven't done the camping thing there yet, and
was wondering, are the showers/bathrooms overly crowded in the
morning? that is, do you have to stand in line just to get inside?
Not having that PA system sounds nice, as do being closer to the
services. I guess up there, you're out of walking distance to the
show.