small block chevrolet in a 68 barracuda headers

I don't like to see Ferd, Chuvvy, Stupidbaker, or Audi engines installed in "my" old Mopars

But the serious answer is this:

Get a set of headers that fit the Cuda body just as if you were putting in a 340

Get yourself a set of blank Chivvy flanges.

Cut the Mopar flanges off the Mopar headers, and after CAREFULLY determining the angle of the dangle, weld the Chivvy flanges to yer Mopar headers.

I used to run CHEVY headers in my old Landcruiser Fj-40 variously had 360, 340, 318 Mopar smallblock in the thing. So mine had Mopar flanges welded to Chivvy SB headers

This is an easy mod, and you can either MIG or gas--weld the flanges, or even braze them.