What you are looking for in that 440 isn't in the exhaust.
You need to remove any smog equipment, add a good carb. a torque cam and converter, proper rear gears. Add some compression and your GOLDEN.

You want quiet?
Go stock replacement.
Bigger may be sound like more fun, but isn't necessary for your needs.
Same for fancy mufflers. Stock replacement will work fine.
That 440 should have loads of torque on tap.
That's what your looking for, right?
You can do a y pipe in front of the rear axle for the dual look you want. It won't help performance though.
Any competent muffler shop should be able to accommodate you.