Years back a friend put triples on a '68 Mustang with a cammed six cylinder. If you are old enough to remember, those sixes had their intake manifold cast together with the head.
Luckily, blaze and some flanges allowed the additional carbs to be added to the original center unit. The nice thing about this was a progressive linkage that allowed you to run off the center carb for most thing and cut the other two in where you wanted. A pair of shaft collars could be moved which facilitated adjusting where they cut in.
Always liked triples. SU’s have 4 moving parts, an advantage in my book. I’ve several cars with Webers from the 50’s and 60’s. The “toolbox” I have containing the parts needed to keep everything happy…about $15-1800 in parts. They look nice but I’d rather have an SU.