I have the headers that came with, but not on, the new-to-me slip-ons, so I plan on just measuring up to those to determine where to make the cuts.
I have absolutely no idea what you're talking about when you say "doughnut for the pipes... kinda an asbestos looking gasket", so I'm going to say "no", unless it might actually be in the inlets of the slip-ons?
Thanks,
Adam