1) Would i gain anything from having the GTD head ported and polished? I am aiming for around 25-30psi boost. Or could i use the "Apparently " better 1.9 AAZ head? if so, will that bolt straight on? I have a 3 notch metal gasket and 12mm ARP studs.
2) What clutch size, and what would be the best type? The GTD engine will be bolted direct to the Stock 4-Speed box, i have found many different sizes (190mm, 200mm and 210mm)...
3) Does anyone know what size and pitch the thread is in the sump? I want to get one of those magnetic sump bolts...
4) What would be the best oil to run, 5w-30? It has just under 100k on the clock.
1. Yes you would, but the AAZ head
IS better. The AAZ head flows a lot better, and if you do some porting/polishing work on the AAZ head, you will never look back. You'll get the same power with lower boost that way, meaning better reliability, simple as that. And yes, it will bolt right on, since your Passat engine is a hydraulic lifter engine.
2. Get a 02A gearbox. You can find one with suitable gearing from mk3 TDI, or Passat TD / TDI. It's pretty simple to swap it on, and the 02A is much nicer to use, much stronger and allows you to use the popular 228 mm solid flywheel, for which there is a multitude of good clutch packages available ( which can not be said about 020-family boxes).
And, if you decided to try it out with your original 4-speed box, you'd realize in a day why everybody always swaps in a long-ratio gearbox

The 4-speed will not work with a tuned engine, period.
3. Nope, I'm looking for one too, best just to take the bolt with you when you go out to buy the magnetic thing.
4. 5W-40 fully synthetic, with API CF rating at least. Steer well clear of the 0W-30 "long life" oils, and 5W-30 "old school" mineral oils have no benefits whatsoever, to merit their use. They should never be used on a turbocharged engine. Best bet is to use a diesel-specific 5W-40, like Mobil Delvac, but there are good options out there.
EDIT: Are you sure your Passat is '94 AND 1.6 TD? I thought they'd all be AAZ by that year, but yeah, the engine on the video definetely is a 1.6. But anyway, you'll find all that you need for your gearbox swap on that very Passat! Just take the pedals, gear stick + cables, master cylinder + bracket, slave cylinder plus fluid line and reservoir, and you're good to go! You might even find a suitable clutch assembly on that Passat, just make sure it has a solid flywheel. You'll save a bucketfull of money if you can use all the Passat stuff without having to source the parts separately! There is only a little custom work involved with the gearbox mount, and drive shafts, other than that it's quite simple.