SU (used on numerous English cars, also Volvos), Stromberg (Zenith-Strombergs conceptually similar to the SUs, used on numerous English cars and Volvos, not the downdraft Bendix-Stromberg units used on some Mopar engines as factory equipment), Hitachi (SU clones used on six-cylinder Datsuns)...
You can see a few different triple-sidedraft slant-6 intake manifolds
here. Pretty sure I already sold all three of these. They all take SU, Hitachi, or Stromberg carbs.
Then there was the
factory sidedraft carb setup: one Carter YH 1bbl (similar to the carb used in pairs on the turbo Corvair) mounted on a flange on the outboard driver's-side face of the intake manifold, where the EGR valve was on '73-up intakes. This was used on the Clark Cortez FWD motorhome of the mid '60s. A cover was bolted to the normal downdraft carb mounting pad. This cover accepted the intake end of the PCV valve hose, and it had a deflector sticking down into the middle of the plenum, in the flow path of the sidedraft carb, to prevent the middle cylinders running rich and the front and back ones running lean.