OldIHC

Anybody have the perfect recipe for making 'em? Or some for sale?

Using TWO ex. manifolds you can slip a divider between 3 and 4 and then braze on second exhaust outlet. It just isn't rocket science. You can buy the wire in a roll (expensive) and run it through the mig welder.
Or..I had a shop plasma cut a heavy flange and i welded on sections of old roll bar and tapered driveshaft until I had made a header.,
Again, not rocket science.
I then put a baffle in the header from an old performance muffler.
You can do it. This old man did.

Voila! A few nights after work...
This is on an IHC 345.