360 la headers & straight pipe

You want loud?
you need high-energy in the exhaust. It's just that simple.
A trumpet on the end of the pipe is gonna make it ugly.
To get loud, you need;
high cylinder pressure together with
an early-opening exhaust valve;
or a really really short, small-diameter exhaust pipe.
My car has a 3" full-length dual system. I am a streeter.
I have run 3 different cams at three different Scrs, 4 different Dcrs, 3 different cylinder pressures, and 2 different exhaust opening angles.
they were all loud at WOT.

But when Not at WOT,
I'm gonna say, the loudest was with the earliest opening exhaust.
The cylinder pressure varied from 176 minimum to 195 maximum.
the combo that made 195psi had the latest opening exhaust (108*) and it was the quietest.
the other two opened at 102/103, with cylinder pressures between 176 and 179 psi, and they were both louder, altho I can't say which cuz they were 3 or 4 years apart.
The loudest was after I cut the H-pipe out.
The least Dcr I ran was 8.77, and the most was 9.27, and the difference, IMO while not remarkable, I'd say was very very noticeable.

My feeling is that in your 360;
with barely 8.1 Scr and a factory 2bbl cam, if that's what you have, the exhaust valve does not open until 116* ATDC and the cylinder pressure is likely to be less than 126psi with a measly Dcr of ~6.77 .
Point being, there is NOT much energy being created on the compression stroke (126psi), and nothing left in the Exhaust, when it leaves the cylinder (at 116After), nevermind when it comes crawling out the tailpipe, having been cooled by some 24 total ft of steel pipe.

For power production,
any back-pressure at all, will negatively affect the strength of the scavenge signal, and reduce the tug on the plenum during the overlap cycle. For an engine with enough overlap to count, Back-pressure is bad for power.
However, while cruising on the hiway; a lil Back-pressure will help reduce the efficiency of the overlap cycle, and that will increase the potential for decreased fuel-consumption; atta time when max torque is not required.
But IDK how you would go about engineering such a system. Well I do but............. when I mention that I once got 32 mpgs with a 335hp 360, people usually call me a liar, so I won't say. The point being; that with headers, overlap is bad for fuel-economy, BUT WORSE;
is an early-opening Exhaust valve. For economy, that 360 2bbl cam with 116* of extraction is right where it needs to be.