how far do i go

[deezee]

ZX9R carbs will work fine with both engines. You'll need them rejetting on the Zetec though as it flows more air/fuel through the head ( I think most people just re-drill the jets up to 1.7mm). Obviously a bespoke manifold will be required for each engine. This isn't hard to make, but if your not happy making one, companies such as bogg bros will sell them.

Depending on your engine management choice, your going to need some sensors. Now I believe, that some early ZX9R carbs came without a TPS and would require a custom bracket and a TPS sourcing. So its just easier to get a later model set, that includes a TPS (assuming you need one)

I don't know if your 1.8cvh is pre cat or not. If it is, then putting carbs on won't make any diff to the IVA.