Those look like cast manifolds - it would be hard to change the dump location on those.
The ones I'm thinking of look like these off the first gen Corvette with the LS1 motor-
https://www.ebay.com/itm/Corvette-LS...0AAOSwr6dejzTJ
They are a double wall construction all the way down to the dump flange but you can weld a new flange on them - they're stainless tube, not cast.