I work for a Foam manufacturaing plant and i used dence lightly convoluted "egg grated" foam and lined the whole roof piece. and looks good too!!
and for floors i used a 1/2" felt pad material cut to fit the whole floor around pedals and seat / brake brackets. then a layer of dense rubber carped padding, then some nice car mats on top of that
wow talk about a drop in cab noise!!
next it the back / side interior walls and interior firewall
havent decided if im dooing the door yet or not
Sure it might not be as nice or effective as the specialized products,, but
its all free!!
I say try your local carpet/ flooring store and look for scrap of these things its free and effective!