Holley did make a replacement carb with small primaries and big secondaries for the Quadrajet which I believe would also work as a Thermoquad replacement. Don't know if its still made though. I also agree the Thermoquad is a good carb if you know what your doing with it as they work great when done right.
I believe Mopar Muscle tested the Demon Thermoquad replacement they make about a year or so ago in the mag and it worked good. I have heard that Demon carb shown in this thread is a good working carb. Ron