Flathead header??

There were several that were made over the years. I stock one that we used to be able to get from Brute Power Pipes.
They were pretty decent actually - very good bottom end (as is the case with most loops) maybe better on bigger tracks where it got the end of the pipe back behind the seat in a low pressure area.

If you need one, give me a call, we'll make you a good deal on one. :)

Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cuts