I mean seriously, when you can EASILY make a J pipe with the stock slant 6 exhaust manifold flange on one end and a T3/4 flange on the other, why would you need anything else?
Iron log heats the intake manifold since they are bolted together. Just removing the heat flapper door helps a LITTLE but not enough for Hi Performance NA or TURBO.
But you can machine the iron center section down and POOF, turbo exhaust manifold.
Plus, a little power gain in port timing by matching the firing order into 3 + 3. Not a lot but when you are talking a little free power here and there......
On the Iron log we split years ago and brazed a steel pipe on each set of 3 cylinders it was OK until we started running 5500 RPM for over 1 minute and the whole log was glowing bright cherry red. The 2 J pipes all the way to the turbo was dark cherry red too.