Quiet, mellow mufflers?

[69hugger]

I need some help from those more experienced then me on muffler selection. This is for my '56 Chev pickup with a hot cam LS-3 and a 6L80E. I bought it with a horrendously noisy exhaust system. It had terrible harmonics, and it was torture to sit in the truck at idle.
I just had the entire system replaced with mandrel bent 2-1/2" stainless pipes, H-pipe, and Magnaflow 18" long mufflers. As the truck has a C-4 IRS suspension, there is no reasonable way to exit it at the rear. The exit is out the sides, ahead of the rear tires. The old system had turn downs, but it was blowing dirt all over the rear wheels, so the new system has straight out square tips.
I "auditioned" the Magnaflows, but the shop was in a metal high-roof building and what I thought I heard inside is not what I ended up with.
The new system is at least as loud as the old system, and with any reasonable throttle, it is way noisier. The harmonics issue is gone, but I don't think I can live with this. I have the Camaro with Flowmasters as the in-your-face vehicle, this one needs to be a quieter, mellower hot rod.
So I am looking for recommendations for a QUIET muffler. Performance is a secondary consideration.
Thanks in advance for sharing your experience!

Bill