I tossed my set of hedman shorty headers in the swap meet pile after I got tired of the flange torquing on me. Could not understand why they did not use 3/8 flanges on those.
On the knock-off replacements I used the stock style three piece exhaust manifold gaskets. These come in the Fle-Pro rebuild gasket kit. They are the aluminum looking perforated pieces. The part number is MS9275B.
So far I have not had any issues with these. A lot cheaper than some of the other options and simple to install.