Thermoquad vs holley vs q-jets

Sounds like you'll be having to run a square-bore if that Speedmaster intake is what I'm thinking it is (Eddy Air-Gap copy).

I've messed with TQs in the past but the last one I put together from 3 cores ran kinda crappy, always had a bad off-idle stumble. I bit the bullet and bought a new 750 street demon and never looked back, somewhat similar design but you can actually buy new parts for it. I think you have a better selection of cores than I do though mine were later ones (1980s) with extra emissions junk. Some day it would be nice to get a GOOD one and make it work but dang, their sophistication is a double-edged sword it can drive you nuts. Reference material is essential for those they're like black magic lol (not really but you know what I'm saying)