What the......???????    you are either really funny, or  somewhat
demented..   LOL
 seriously hope you are joking.

In a message dated 2/15/2016 8:51:08 P.M. Eastern Standard Time,
olgreywoof@GMAIL.COM writes:

Roof top  box, with some special considerations.  You'll want to drill
extra
holes for ventilation, but size and place them carefully to  avoid
turbulence or ingress of inclement weather.  Have a cushy bed in  one corner
for him to curl into and snooze, and carpet the rest so he can  roam and
pace with sure footing.  Provide an assortment of small toys  so that some
of the roaming is somewhat less mindless. Spill-proof water  device of
course and availability of dry food.  Litter box in a corner  farthest from
the bed.

The space between the bottom of the box and  top of van will provide a good
measure of sound deadening, but you should  probably check out your sound
system to be sure the volume can be raised  sufficiently if necessary.