If you use the TT gearbox you need to find out what ratio final drive is in the gearbox.
You then need to find which rear diff will match to the front final drive.
One of the bigger questions you need to figure out is how you will control the 4WD. Do you want to keep the completely mechanical viscous coupling of the Syncro system, or do you want to install the Haldex system from the Golf/Skoda Octavia/A3/TT? There are standalone Haldex controllers available, but that’s going to make your install a lot more complex.
Given that the engine mounting in the Golf1 is completely different, how do you plan on mounting the engine and gearbox in your Golf1 platform?