Free header flange slant 6 and T3 flange for dfx file

You are actually looking for a DXF file, not a DFX.

Don't have one handy but it would be pretty easy to reverse engineer from an actual head or even a gasket.

If it was me, I'd find out what brand of exhaust gasket is most accurate and go from there. I'd also be tempted to split that long hunk of torched metal into two pieces to allow for expansion. Maybe cut it in one piece and cut it in two after burning it out. Or, weld the header together then cut it after. On the other hand, a tubing header would be more forgiving than a stock cast iron manifold regarding movement.

Good luck.