quick help

[Captn. J]

i m a lil stumped which one i need    my headers has  1 5/8 ID but 1 3/4 OD   so i m trying to buy right 4 to 1 header collector     do i need the 1 5/8 one or  1 3/4?  here s example
http://www.ebay.com/itm/Hooker-Headers-11522-Mild-Steel-4-into-1-Collectors-/310917962438?pt=Motors_Car_Truck_Parts_Accessories&hash=item4864279ac6&vxp=mtr

[MR NASTY]

I would think the one that matches the od dimension

[4x4xdodgeman]

od dimension