I was considering doing this for a laugh on my 2.0, (as the bottom end on mine can't even take normaly aspirated pressures...)
You'll have a few issues, as mentioned, management & low comp pistons, (I think you could run as high as 9.0:1 CR), the one that'll limit your power gain (in my opinion), is the cam timing - too much overlap, (& I don't think it would work well with a variator), to allow any more than 5 or 6 psi of boost. To make it worth while, you'll need to get some softer cams, that'll allow you to crank up the boost for a bit of fun!
Cheaper and alot easier to get a v6 for the extra power.
I would like to see it done though, so get some tube and a welder and crack on!