What I did not see other than it is a 80 with a 300 six / 4.9 motor.
Do you still run the factory log exh manifold?
Will you be running a cat or 2?
Will you be running a full factory exh. system, maybe less cat(s), but tail pipe all the way out back like the factory system?
Long or short bed truck?
I ask because any and all will change the sound that comes out the end pipe.
When I first got my 81 F100 short bed truck on the road it had EFI manifolds and factory Y pipe.
I did not run a cat but did run a factory round muffler and tail pipe out behind the tire.
I got to say when running you could not hear it, way to quite for me.
A year later the inlet to the round muffler started to pull out so I replaced the full system from the Y pipe back (94 F truck system) but I went with a Thrust welded oval muffler, its a bolt on from the parts store for the truck, no cat.
At idle I think it sounds like a v8 with a nice muffler, cant tell you what it sounds like at speed when outside.
Inside you can hear it has a different muffler, it is not loud. How loud can a straight six be?
Dave ----