Thank you for reply and for sharing your version of script.
Although in the meantime I reconstructed frontal faces by hand, it was easy and it took less time than I expected. I deleted faulty edges and polys, and using cut part of cylinder and remaining vertices I've drawn edges and filled them with triangles. Resulting output from your script closely matches the version I've done by hand.
Your version of script looks to be a bit slower, but it better preserves texture coordinates and it drew correctly almost all of faces at first try. The triangles that hasn't been drawn were the ones that had very large angle between arms, or the ones having arms of almost equal length (I don't know the method used). It's the case where vertex from the first mesh is placed near the (center of) edge of the second mesh. The script I've been using failed with some of the examples from *.an8 file you've attached (non planar faces of spiral?)
Thank you again for your time! I think that my specific case can be closed, but if you want to investigate boolean scripts, then feel free to use this topic.