It is no biggie. People are scared of TDI wiring for some reason. Most of the time its just people not knowing the full story.
For a 1Z/AHU swap:
-68 wires to deal with
-do not need a cluster at all
-brake light switches and clutch switches can just be grounded with no ill effects
-you do not need the VSS at all
-stuff like the fuel gauge and such are not tied in with the ecu
If you want to use the factory cruise control which is built into the ecu you need to run a VSS and have correctly working brake/clutch switches but even this is no big deal. If you just do nothing with the switches you get a blinking GP light.. thats it.
I have a AHU in my 1986 4Runner. The ecu has no idea its not in a Jetta anymore.