Yes, a photo of the intake side will help, as will a photo of the air cleaner with lid off (so we can see the carby flanges that bolt to the air cleaner
Yes, they can be used on a A-series manifold. British SUs and Hitachi side-drafts used the same mounting dimensions. Apparently the metering needles can interchange too which is good since it's hard to find the different Datsun ones
Some other interesting bits:
* Looks like 4-bolt flange carburetors. The 240Z had that type, but they are much larger than the 4-cylinder carbs (1.75 vs 1.5 throttle bores). The
A14 factory twin carb setup used 4-bolt carbs, but were flat-tops -- and had traditional electric chokes out the sides
* I think some british SUs were 4-bolt type, but are less common. We have photos of these used on A14 manifold, but I don't know what car they are originally from. Maybe Volvo or MG
* that air cleaner looks factory, but not Datsun. The stampings are more intricate than any Datsun air cleaner i've seen. See
Hitachi Twin Carb Air Cleaner