single exhaust system design

[fleetman]

I have shorty jba headers 2.5
Motor is 350/400 . autotrans, lowered bags, dropspindle.
Tentative plan is to have 2.5 pipe fabricated.
into a flowmaster 2.5- to - 3" scavenger.
Here is where i am stuck.
Because i want a not loud single muffler round about 6 or 7 " in diameter.
Exit pipe location as stock, size probably 2.25 or 2.5.
I am having problem finding a muffler that might work.
Or maybe there is better way to do single ?
Thanks
Paul