Does anyone have ideas/suggestions for constrcting a pretty-much airtight partition to separate the cargo are from the driver and passenger area on a 1998 3500 series van?

We utilize the van and need to separate the chemicals and small engine (runs only when no one is in the van) heat from up-front.

Also, would like to install a 4-speaker--two in doors and two behind seats stereo system with a 4-channel amp and some sound deadening. The van has been armorthaned on the interior about two-feet high, including the front passenger areas. The doors, floor and roof in passenger area would surely benefit from some noise reduction. How about the doghouse cover as well? It's a 6.5 diesel.

Any comments and suggestions on these topics--pics welcome, would gretly be appreciated!