There would be no need to put Golf3 trash like a complete subframe under it.
Even with the wide-track conversion you don't need to install a Golf3 subframe.
Brad as ever over-reaching himself with his interweb nolidge.
The most simple thing to do would be to use G60 mount at the back, on your current subframe, with a 1.3 (solid rubber) gearbox mount and a GTI-type mount at the front. If you're using a cable-change gearbox you will need the correct flywheel, tinware and (importantly) the front mount bracket, plus driver's side driveshaft to suit the width of track you're using.
I would also supplement this with a pendulum mount to the gearbox to keep the movement down on the set up.