Smog tests are a good way to test a carburetor. Your goal is to get as high a CO2 percentage as possible. High CO means a rich mixture. High HC also means a rich mixture or worn rings. High 02 percentage means a lean mixture. High NOx means high combustion temps, which is a good thing. If you like, I can post some links to mixture/bi-product graphs.

I think my 3.73's are a good all around gear. I get over 12mpg on 6050 gvwr truck while driving at 65 mph without overdrive with a 350.

6050 gvwr is great because the 95db max sound limit only applies to vehicles under 6000 lb gvwr. Not that my truck is louder than 95 db