Okay, I am probably going to get made fun of for this. I don't like loud cars. Well, for 10 minutes it's fine. 3 hours? Not so much? 8 hours? No way. And I don't need every homeowner I pass giving me the stink eye.
What are you MGB guys running to take the drone out of you car? Stock?
What motor?
Rover 4.6 ??
On my Rover, I have a Hooker Aerochamber.
Some on here swear by the Thrush Turbo.
Ivor
I'd suggest starting with this article... http://www.britishv8.org/Articles/Muffler-Selection.htm
You might also enjoy reviewing the HIWD archive, to appreciate the tremendous variety to exhaust systems on conversions: http://www.britishv8.org/British-V8-How-It-Was-Done.htm
I do like my dual Thrush Turbo system, but I wouldn't call it quiet! Combined with my cam and my tri-y headers, I think it has a nice tone. My little Buick 215 sound "bigger" than it is. It's interesting that you mentioned the homes you pass. Exhaust sound is more directional than most folks appreciate. My car was much more obnoxious when I had exhaust pipes aimed out the sides (ahead of the rear tires). Pointed at the ground is more polite, but more noise reflects back into the car.
You can listen to the varijusThrush offerings online, here https://www.thrushexhaust.com/hear-it-sounds-of-thrush/
Ivor
I had Spintech Cruisers (under the seats) with 10" glass packs just before the tailpipe exits at the back of the car on my 302 and it was pretty quiet. I actually switched to Dynamax mufflers to give it a little more aggressive sound.
Earbuds.
I have a factory original 79/80 MGB muffler if someone needs one.
VV.mg.mgb.muffler.jpg