Carb to Injection

as above, MK3 Polo lift pump fits the carby tank. its the same as the one fitted to later cabby + scirocco. any MK3 Polo will work, they all use the same lift pump. Make sure you get the plastic reservoir under the car from the same model, this will prevent fuel starvation round corners.
then you just need a suitable main pump to match your application. for a MK3 GTI lump you can use a MK1 injection pump with a banjo barbed fitting adaptor, easy to get from ebay. alternatively can use a Polo GT or G40 main pump, I'd also get the fuel lines from a MK3 polo as well they're made of plastic. your old metal lines will likely be buggered. MK3 Golf lines might work?

The MK3 Polo is a good donor for the above as it also comes with a bracket and under car fuel filter, all mounted in a line so ideal for a MK1 chassis. obv mk1 cabby/rocco would work too as they're again mk1 chassis. if you get a MK1 pump setup you dont need the fuel accumulator, just get a barbed banjo fitting as above and push on a std fuel injection rubber fuel line onto it

as above, carby tank is not gravity fed, that's the GTI tank. most if not all electric pumps will struggle if hooked up to carby tank, plus as i say on corners you'll suffer from fuel starvation. fuel pumps dont like running dry either it buggers em really quickly. also the proper GTI tank has a swirl pot in the middle of it connected to the outlet at the bottom, this prevents fuel starvation.
some of the cheapo gti tanks dont have this, so if you do go for a gti tank make sure it has a swirl pot! then you dont need the lift pump & reservoir, just connect pump direct to side of the tank.