Glen,
I don't know which gaskets are being used. The engine is a crate engine installed by the previous owner. I do have a lot of the receipts from that rebuild and if I can find the time I'll dig through to see if the gaskets were spelled out. Since it was a crate engine I would think the header gaskets would have been purchased separately instead of in a kit.
I don't know if the Banks headers have heavy flanges or not. To be honest this has been an area where I haven't had to worry about anything because it just seems to work/seal just fine.
However on our Argosy engine installation that is something I DO have to worry about so information like you provided is priceless
Brad