Hi, im doing pretty much the same with my GT2, check the projects section. Although mine is an ACE coded engine from an audi, which is very similar to the 9a.
The engine will drop straight in, the clutch from the 8v and the gearbox will both fit.
You will need the engine mounts off your 8v though.
You will need to get the 16v alternator brackets and alternator if the engine does no have them already.
Water pump from the 8v will also bolt straight on if the 9a does not have one.
You'll need the ecu and wiring loom from the corrado.
The exhaust is the hardest part in my opinion, dubpower do one for a mk1 golf which fits (
http://www.dubpower.co.uk/).
You will also need a fuel injection pump.
You may also find that the distributor fouls the brake fluid reservoir, i fixed this problem by using an ABF distributor cap (with the 9a you may need to get a whole new distribtor though as i think it has clips to hold the cap on where as the ABF/ACE have screws.)
Thats all i can think of atm. Hope this helps
