to answer your 9a questions, you have to use the gti pump as the 9a managment is still based on k-jet, so needs a proper k-jet pump & pipework. all the isv wiring etc is all contained within the 9a wiring, so just a case of stripping it and splicing it to the mk1 fusebox. Not as scary as it sounds, once you strip out everything that isnt connected to the ECU there isnt much left to worry about! use as mich of the mk1 engine loom as you can, i.e. sensors etc, just bin any carby specific bits, then combine the 2.
if you were planning on using the abf inlet to run on 9a managment that wont work, but if you mean you had a abf inlet modified for carbs then thats fine
when you go for the webbers you'll need either a KR ignition control unit and loom to do the ignition on the 9a dizzy, swap on a vacuum advance dizzy from a 1.3 MK2 or I think a pug 1.9GTI one works quite well, or go for aftermarket ignition managment of some kind.
