Thermoquads were not all the same. In the later years, they had lots of "additions" which could be difficult to calibrate and such. I bought a 9801 TQuad for my '67 Newport 383 4bbl car. That particular part number aftermarket TQ was allegedly tuned for a '70 383 4bbl engine, which had the same cam as my engine (which already had 906 heads on it). Even with the Torker 383 intake, not very much difference compared to the OEM AFB and cast iron intake.
IF you like the look of a TQ, buy the Street Demon with the phenolic bowl. Inside, it looks just like the TQ it was patterned off of. Just need to get the throttle linkage adapter to make everything work. Watch the sales at Summit or Jegs.
Otherwise, an AVS2 would be my choice. Then head over to "318 will run" on YouTube and look at his modification of a Chrysler cast iron spreadbore intake so that a non-spreadbore carb will fit. EASIER than you might suspect! Then add the thick OEM carb gasket and you're done.
When the TQ came out, I was all for it. Some people had issues with leaking phenolic bowls, others did not. But as the emissions controls were added, things got flakier, it seemed. More "stuff" added as time progressed. Nothing really wrong, per se, but consider that it was not one of Chrysler's best fuel mixers, too. It was Carter's "last gasp", too, so not a really god end product, in many respects. The basic design MUST be good or Holley/Demon would not have copied it so closely!
In general, a new carb will be better than an older OEM carb. Reason? Additional tweaks and such to the primary venturi area which can increase throttle movement sensitivity. But are not apparent to the casual observer, but make things a bit better to drive. In THAT area, the TQ is still later 1960s technology (as the Rochester QuadraJet spreadbore came out in about 1965).
Several decisions.
Enjoy!
CBODY67