I went to a online distributor of tractor trailer exhaust pipe.
they have chrome stainless in multiple sizes.
Unfortunately I dont remember the name of the place but any like Peterbuilt or Mack truck type of places will be able to help you
My 4 pieces of 4 inch stainless were like 25 dollars each for 20 inches each if my memory serves me correctly
Whole thing ran me about 100 bones
Had to cut them down
But if you want to do it really right
contact Outer37 here on the board
he has for sale a staggered setup of dry pipes and Gil manifolds he is selling.