Hmmmm, I'm not really sure removing the deck and mirrors will improve you mpg that much. It's a pretty bulky front end already. But, just my opinion.
From a cosmetic perspective, and ease of washing, I can see getting rid of the mirrors altogether.
Yep, time to go high tech with rearview cameras! Seriously, they have kits for side cameras that will display on a screen, and can include a dashcam and a rear cam.
If you want to go a more traditional route, these are listed as GMC Savana 2500 Van with Commercial Cutaway Chassis Driver & Passenger Side Manual Manual-Folding Textured Black Towing 2 Piece Mirror Set
Hope this helps.