Havn't heard of doing that before.

What I want is quiet. Like, ninja quiet.

What you're suggesting is having a resonator and a muffler?

 

Why not run two mufflers? Not a perfect solution but it will be quiet.

 

Two works great. I ran a glass pack as a pre muffler and a standard turbo type main on a hunting rig and could listen to the mechanicals in the engine working even under a load. Stealth it was.

 

stock 99-07 ford powerstroke muffler. 3.5"

 

How much more over stock quite did the OP want it?

I am also running the EFI manifolds, Y pipe, stock carb & intake, no cat into the stock muffler & tail pipe for my 81 F100 and it is pretty quite.
I think if I was running the cat it would be even more quite.
Dave ----

 

You people are way over thinking this IMO. Get two cheap barrel style mufflers from an application that makes way more horsepower than a 300 (e.g. a newer truck or van) and run them in series.

The side should satisfy the "not restrictive" criteria and since you're not mass producing the setup buying two cheap mufflers is still cost effective.