Steering Boss

So I'm considering getting a Sparco steering wheel. I've been looking into it and it would appear that most after-market wheels have the same bolting pattern so all I'll need to get is an Escort Splined boss, Is this correct?
Is there a difference between the MK1 and MK2?
I'm assuming for ADR regs I'd need a collapsible one?
What bosses are some blokes running?