If you have the 1.4 engine running on a carb, why not get a an XR3 carb and use the 1.6 engine with that, no wiring issues or fuel tank changes. That way you can then gather all the parts you need to do the conversion you want all in one go, not in bits.

Personnaly i would go for a modern after market managment, ie DTA, emerald, omex etc.. offers a far better scope for future tuning options, ie if you start off with an efi inlet, then decide you want big ass throttle bodies with injectors, this can be mapped accordingly. With K or KE jet you are going to be limtied as to what you want you can achieve.