Here is a stock Ford Flathead, and yes the stock manifolds were horrible. Were they "good enough", yeah, for a grocery getter it did the job.
But for a mild hop-up, it got something a little more like the modern header.
Most common for a race car was "zoomies".
Here is a modern hot rodded flathead.
This is an interesting example of a Flathead Ford, and pretty common. For the very high performance motor the exhaust is ran out the top of the motor! You can see the un-used old exhaust ports on the side. Another thing they used to do was to run the motor in reverse so that the exhaust was the intake and vs-vs.
I have looked it over pretty well and building a header flange from a piece of tubing is going to work fine, and the flanges on the block are plenty strong. I only plan on making short header, no equal length or anything like that.
Brian