G6Dub already have a 20V mk1, as well,
yes have 20v in mk1, you need custom engine mounts, and as far as I know I am the only person to have the 6 speed box so far as there is a lot of custom work to get it in there, so most people use a G60 box.
I am in the process of doing a mk1 caddy it will again have the 20vt and 6 speed box.
The best way I think to do it if doing it yourself is to buy a complete car i.e a crashed one then you can use everything, I have all teh 20v wiring etc... all going in and it also sorts out the costly imobiliser troubles everyone else is getting, as you can use the original ignition and key.