what's involved in converting IRS to swing? Get a super diff, some axles, the tubes etc?
Convert IRS to swingaxle? Usually it's the other way around but since you asked:
I just did this conversion but in reverse. Correct me if I'm wrong here guys but IIRC this is what you'll need:
A swingaxle tranny (duh) complete drum to drum (tubes,axles etc)
Swingaxle spring plates,bushings and caps
Swingaxle torsion bars - can't remember the length though.
You're also going to need to buy new rear hard brake lines. Not sure about the rubbers though.
And since you're planning this swap try to find yourself a tranny (or axles/tubes and drums at least) from a type 3 so you can use the bigger drums.
If you do end up finding a type 3 swingaxle you'll have to swap the nosecone to make it work in a beetle. But that's the easy part.
Good luck.