Hey Guys,
I'm also looking for the "SU" GX manifold (have been for awhile now). Please post info on possible leads!!

As for using other carbs on the SU manifold such as real Skinner's Union carbs (MGs etc), there are a couple of things to consider. I've found that if it's an HS4, 1.5" bore it will have the correct mounting holes, ie 3" centers at 45 degrees to the vertical (or horiz whichever). But the GX manifold has the 45 degrees running the opposite directions so you have to make sure the carb pair you find run the opposite directions. To help clarify that, on the GX the bolt angles are something like \ / vs / / or \ \ for some carb setups. On the other hand, i've seen very simple adaptor plates that can be used to bolt any carb pair to any manifold. It's basically a square with 4 holes at the 45 degrees spots on 3" centers. But you still have to be careful that you can fit the carbs to the manifold if they're not mounted in the preferred direction ie with the bowls facing "out" or away from between the carbs. Also there is something else to consider. Some carbs were designed to be mounted to the engine at 20 degrees or 30 degrees, so their float bowls will be angled to keep the bowl level when the carbs are mounted. I've heard that you can replace the bushings to set any float bowl from an angle back to 0 degrees, but I haven't tried it. As for linkages, you're on your own there. I'll figure that out when I get to it!

I don't know if the 1.25" HS2's will fit without an adaptor. The 1.75" HS6's are 4-bolt carbs on 3" centers (I just measured my Z carbs). So they will bolt up but only with 2 holes and the bores won't match.

Oh one plus to using real British SU's is that they have a LOT more performance parts available. Much wider range of needles etc. That's what I've found in my research anyway (which I'm still working on...)

michael