I'm still going with my car based on an MX5 (91) 1.6 donor. I'm looking at the exhaust, particularly the downpipe to Cat connection. I'm using the standard flanges, so I was hoping the gaskets would be easy to replace.

However I have doubts on whether I have the right gasket. MX5parts supplied me with a flat gasket which physically fits, but looking at the profile of the pipe it looks like it should be a 'donut' style gasket rather than a flat. There's even a comment on MX5parts about the gasket that suggests the same. https://www.mx5parts.co.uk/catalytic-convertor-gasket-mk1-front.

Problem is, even though it looks to be a donut, I can't find anywhere that supplies it. What would be the best thing to do, stay with the flat and hope it seals ok, or try and source an appropriate donut?

I think a donut gasket would make things easier for me, as they seem to tolerate misalignments better than flat gaskets.

Have you tried a local motor factor? They probably want the original reg' but the rings are common across many Asian cars so should be possible to find from its dimensions.