I have a few sets of 340 manifolds so I ported a set of 1973 ones.
I have Super Comp Headers now. And the plan was:
Headers, 2.5" X -Pipe, Cutouts Muffs and tailpipes.
But thinking of a Motor Swap.
And:
Ported 340 Manifolds, 2.5 Head Pipes,
But Should I use Dr. Gas X Pipe? Should I still put the Cut Outs? How Bad could It be like that?

Blasted Painted and going to Machine Shop Tuesday to get Gasket Surface Milled Flat and Smooth.

So....what are you asking? Is it about power manifolds vs headers? ex leaks? what? everyone knows (I think) that you give up power with manifolds and headers leak.

Even "ported", you'll still be down 15-20 hp or so w/ the manifolds vs. headers.
GOOD headers don't leak. I've had issues w/ every set of Hooker headers I've run, but not TTI.
The X pipe makes power, no denying that, but the sound changes w/ it. It gives a higher pitched sound to the exhaust. Personally I don't like the way they sound, but a lot do.

If I swap to the Manifolds.
1) Should I still use a X-Pipe? Head pipes then X-Pipe that is.
The one I have Can not be used as it was made as,a,3 inch to come off the Headers and go to 2.5 inch.
So would need 2.5 head pipes and 2.5 X 2.5 X-Pipe.
2) Since I have 2.5 cutouts should I use them with manifolds?
As in Head Pipes, X-Pipe, Cutouts. Muffs,and Tail Pipes all 2.5 inch.as,far as,sound wise that is. Not sure how and X-Pipe would sound without Large Tube Header
Or how Cutouts for that matter with Manifolds. With or without the X? Would an H be better?
Asking since I am sure some here have run manifolds and X or H.
And may be silly enough to use Cutouts with out Headers.

Just use what works and an H pipe. The X pipe may be marginally better somewhere, but the H pipe is much easier to find room for, IMHO.

R.