Can you slap on a turbo from simelar engines on a N/A?
Like does the 1.4 GT have stronger engine parts or is it the same as the 1.1 1.2 and 1.6?

Nope
You be better buyinf a new car

You can just stick a turbo on a car with electronic fuel injection and expect it to run without massive amount of work both physical and to the ECU files

the GT has a completely different engine entirely to the 55/60/75/85, they are all fire engines whereas the 90 (1.6) and GT are 8v lampredi engines. Nothing is interchangeable between the engine families.

Modern Tjet engines are the same engine family as the fire engines in mk1's, if you want a turbo mk1 without buying a GT the tjet swap is the most sensible route. Far from the only route but the most sensible imo.

The 1.1/1.2 8v engines take to boost quite well and they are strong but it makes much more sense to just get a tjet these days.