Old Style "Rams Horns" Exhaust Flange Donut Gasket

[Loose Screw]

My exhaust manifold does have a small rim about half an inch down inside the outlet to exhaust pipe.
I've noticed that some exhaust flanges have a metal collar built into them.

I put your typical donut in there (no collar) and it still sounds like it's got a leak. Yeah I did put new nuts and bolts and kept cranking on them but it still sounds like there's a leak and the gasket to head is new. I'm pretty sure it's that donut...

What do you all use on those old rams horns?

TIA