For the engine, you can improve the wings considerably by doubling the image size, then manually smoothing the lower (concave) edges of the gold stripe. Use a line-drawing tool to straighten and sharpen the straight line along the bottom of the top stripe and the top of the bottom stripe. The upper (convex) edges can simply be extended into the rest of the image using floodfill, because that edge is defined by the mesh. That alone is a big improvement. There's a mesh problem at the top of the cylinder that creates an angle in the lower stripe that could only be fixed by running the stripe across part of the cylinder image, and that is extremely difficult to do well. The artifacts on the cowl can be removed by setting the transparency to a constant value across the whole image. Use the value for the alpha at the slots in the cowcatcher. Remove the single pixel holes in the rest of the cowl image area by filling with the same color as the rest of the image. The joint in the mesh at the rear of the cowl will create shadows and lines that cannot be eliminated. The headlight cutouts can be tidied up with pixel editing. I think that the Blue image also needs its alpha set to a constant value. I haven't looked at the tender, but I presume the fixes are similar.
(which is true) and it was an unlisted video, however