detonation / knock issue on 340

If the intake manifold doesn't have the bolt pattern and openings for the Thermoquad, then it becomes a hassle and IMO not is not usually a good match for the intake.
So assuming the intake is for a Holley squarebore with not adapters, then find a used Holley and switch over the throttle extension from the old one. New is not always better, its just new. That said, if you want something new more like an T-quad but fits a square bore intake, then the "Street Demon' is worth looking at.