I had a local exaust shop custom bend a full length exuaust for my Early.
Shorty Bloch Hugger headers Flow Master mufflers 2 1/2 inch pipes exiting out the side BEHIND the rear tires.
I supplied the headers and the mufflers the shop did the rest.
I was very happy with the job they did and the price they charged me.
the system is now 7 years old and it is holing up great.
money well spent......
Pipes strait out the back is a No No for vans.
leaking rear door seals and the pop out windows can let exaust fumes in to the van if you go this route.
GM did there tail pipes like I did mine from the factory.
As soon as I get an engine dropped into my late model GMC van I will do the same exaust in it.Minus the headers