Hey cerial. Don't do what "I" did, which was to weld the pipe to the flanges, and then use flat gaskets to the manifolds. The shop I had make up the exhaust came up with that scheme, and it's leaked ever since.
I talked to Tom Langdon about it and he said not to weld the pipe to the flanges, and to use the donut gaskets that came with the manifolds.
One day, I'll need to redo my exhaust anyway, so then I'll start over with new flanges and gaskets and do it right.