I just measured the length that the cords run on a 1992 Ford EB van. It looks like it needs to cover about 4ft front + 4ft back + 11ft side + 11ft side which is about 40 feet for each bungee/stretch cord. I'm not sure how much stretch you'd put into them, maybe 20%? That would mean you need about 32ft for each cord. It looks like my original cords (if they're original) are 3/8" thick.
Anyone who's done this remember the length they ended up using?
Thinking of ordering this marine grade 75ft long 3/8" thick stretch cord:
http://www.ebay.ca/itm/401040027433