FWIW on several old stationary-type engines I have fitted (28mm?) Solex VW carbs - two of them on re-purposed Bedford engines, for example. They are wonderfully simple carbs with an easily-removed main jet for mixture changes. With the accelerator pump blocked off & vacuum shit disconnected they're a good donor for anything that runs at constant revs with a simple linkage movement. I have just made intake tracts out of exhaust bends