Van exhaust?

moparblood said
Dan, the current pipe that came with the van is 1 7/8 why did they reduce it so small?

Because 1-7/8" pipe costs less. No other reason than that.

so if i just put a 2 1/4 pipe i don't need to change manifold?

Correct. That's what the factory did on the Feather Duster/Dart Lite (and on all Slant-6s starting in '77-'78): bolted a 2-1/4" headpipe to the same manifold they'd previously bolted a 1-7/8" headpipe.