Like Scotty said you can build up a T5 while maintaining what the T5's are known for as lightweight and smooth shifting.
Not all T56 are created equal as the older ones are not the super torque holding monsters you are thinking of.
Also transplanting a foreign T56 you will need a new driveshaft, bellhousing, clutch, amongst other things like trimming and modifying to fit.
2016 VW GTI 2.0 Turbo
1989 Sonic Blue LX Coupe, 349 ci, TW heads, TFS Track Heat Intake, 75mm Accufab TB, 80mm ProM, 30 lb. inj, TKO, 3.73, 31 spline w/ TruTrac, MAC 1-5/8" LT headers w/ H pipe, Flowmaster, electric fan Moates QH
391 rwhp & 424 rwtq...Mustang Dyno 11.5@122mph