Get a big set of boxes like the idiot boom cruisers use and fit them to the
load bed. You might be able to hear them with 500W of power through them as
well :@)

P.

you can build boxes in the rear corners behind rear side seats, ie behind the
rear light area .
build them so they fit in gap between body and the seat base and finish just
under the small window rubber.

this will take 6x9 speakers and give good bass .

I'm planning to build a centre console to bolt onto that gap between the
front seats; that'll all be wired up ready to hold a CD changer, stereo,
comm radio - and speakers.

ours are in the roof lining