This is what i got. This is what i wanna put in it. Any advice would be appreciated

Im not looking for speed. I just want it to be loud. Straight headers to 4" side pipes.

I have plenty of time and money to put in it.
A 360 with 63cc heads, falls together at close to 11/1Scr, ; and
that makes her plenty loud, and
the SBM almost drops right in, and
you get to keep your P/S, PDB, A/C, whatever, and
in your case, (not looking for speed), you can use any old trans/any old rear end/any old gear, but with a SureGrip/Posi in it, and
just Stall it up a lil.
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However;
side-pipes with headers, is gonna be a bit of a PITA, as to plumbing it. Dusters/Demons/2nd gen Barracudas, are 108 wheelbase cars. The header collectors stop at about where the doors start, and that's without any collector extensions. Then you gotta make two 90s back to back, from the collectors over to the side pipes, dropping underneath the frame to get there. By the time you get that done, with say 2.5" pipes, you're getting past the middle of the door, and chewing up ground clearace in a hurry.
So yur gonna have to be mighty creative, to figure the rest out.
I had thought to do this on my car also, but after the TTI's were installed, and 18" extensions, it was just not possible. T/A style side-exits were, but I'm a streeter, and not a fan of exhaust pointing at the guy in the next lane....... cuz I too was planning to be loud. So instead, I just ran dual 3 inchers all the way to the back bumper thru Dynomax 3-pass muffs..... which turned out to be plenty loud enough, at WOT, for me, even with slash-cut turn-downs.
Yes, I suppose, I could have installed Shorties, but that, IMO, using a 360 with a manual-trans, would have been too big a performance-sacrifice, for me. Jus saying and,

Happy HotRodding