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you'll end up with pretty low compression if you use CA16 pistons as they are 5mm smaller in diameter

I went down this track a few years ago, modified the inlet manifold to bolt the 45mm dellortos on and modified a distributor out of a ford telstar to go where the CAS normally goes. Did most of the hard work then changed direction. Still think it is a good idea though, might revisit it at some stage actually.
Why carbs over EFI? It justs suits some people better, probably cheaper for some people, and probably flows better than the factory EFI manifold so should go better!