No exhaust gasket?

I finally pulled my 2-1 exhaust off to paint and there was no gaskets present where the pipes go into the head? Can I use just donut type automotive gasket? If so what is the diameter? I have held my hand there and never felt a leak, I just feel there should be gaskets in there. 1977 KZ750 twin, thanks much, Nate.

They aren't too expensive. You can measure the pipe flange dia. but why not get new ones?
Steve

The gaskets may be stuck inside the exhaust ports --- kinda common.
Z1Enterprises.com has the copper crush gaskets. There might be some fiber gaskets that will fit.

The copper donut gaskets are what go there.