Mate I think the TT head gasket is 1.6mm. 1.3mm is recommended for a good NA-T due to keeping some of that compression. ClubNA-T has information guarding where you can order a gasket set for this size. Alot of people do poo poo the idea of this as you get a squish (don't think spelt that 100%) effect where the chamber doesn't completely empty it's burnt fuel. Almost like dead spots in a room that aren't vented properly due to the chamber and head design not considering the extra width of a thicker head gasket.
BUT saying that, alot of conversions don't have any issues and this can add to det, but your hit 500+ bhp until you will need to address this.
You have two main factors with doing an engine build on a seperate engine, money, and power requirements. Time would be the other main factor, but considering you don't need the engine running your sorted. I was a bit stuck for time so when a problem arose I just had to do whatever it took to get it running.
If you can take as long as you want, money probably won't be a huge issue as long as you don't go silly. So you need to set yourself a power requirement. There are loads of NA-T builds to give you an idea of whats required for what power levels, but on a stock kit your looking at 360hp at least, but if you spend another grand you can be hitting near 450hp if all is well. But your getting close to transmission limits!
I set myself a target of 400 due to not wanting to change my gearbox at the moment. So you need to find out what limitations you have being manual or auto and if you want to keep stock injectors or stock compression, and decide which your prepared to upgrade. stock injectors won't like 400hp for example. stock compression won't like 12psi without water/meth injection.
Don't forget to consider mod's that will safe guard your engine as well, oil cooler, decent intercooling, heat protection via manifold / downpipe wrap or turbo blanket etc (I need to get the wrap myself as I have loads of heat at 373hp on unwrapped manifold).