all will howl at me, but for a good street carb, i just love the Thermo-Quads.
reasonable to good mpg for all engines [WAY better than 5mpg if you keep your foot out of it], big or small block, plus reasonable performance as well.
however, one must be able to tune these things with the proper metering rods and jets [which are somewhat difficult to get at times], as well as adjust the secondary air door properly.
proper vacuum advance and distributor weight [and spring] curve for your combination is also a must when using these carbs.
this is only my life experience and opinion. your MILEAGE will vary.