Is this a question on interchange?? All 221-239 flathead header will fit all years of engine. Fitting your chassis is a different can of worms.
I think they only work if you have the stock stearing box. I have a 39 box and had to bend the pipe to clearence it. The stearing box doesnt seem to get that hot though. I used reds headers for a 35.
I'm using tube headers on my 40 pickup, and they clear the vegamatic steering box by about 1/2". 4TTRUK
My car is stock motor, stock frame and steering box, it looks the only problem will be the steering box, does anyone have any different pictures of headers for Flathead eights?