If the KODACHROME has been cold stored since new, it can still be processed Reversal, either B&W Reversal or Sepia Reversal(a rich brown tone, with some other yellow tints from the film layers). Thus using the filter in the camera with help make cloud detail stand out, or darken down the blue sky from white to a gray tint to render separation [just as in any B&W film photography]. The film ideally should be rated at ISO 10, thus manual exposure to allow normal B&W Reversal processing and obtain the best image quality. However, most still just shoot it at ISO 40 and it has to be push processed nearly 3 stops to render decent image density. You'd think it would terrible, but it still looks pretty good. I'm looking forward to shooting my long expired KMA sound film and B&W or Sepia processing it, as it looks nice if done right. If the film has not been cold stored frozen since new, only at room temperature, then it comes down to how old it is; film over 10 years old will look poor to fair done as B&W Reversal and will yield better results done as B&W Negative (image can be flipped to a Positive upon transfer to digital). Here are some image samples from various tests:
As you can see, they look pretty good, and these are without any digital image enhancement to lighten or darken them.
The EKTACHROME 64T films should still yield fair to good images with reversal color processing. You do have to use the builtin Daylight #85 filter when shooting in daylight conditions for the color to be correct. Any off color after the film is processed, it not too bad, could be corrected in film transfer to digital. I suggest doing a test roll first and seeing how it comes out. That way, you are not out of a lot of money. Dwayne's Photo Lab in Parsons Kanas USA is the cheapest place in the world for E-6 processing and do pretty good work. Even with the cost of postage from Spain, you're still ahead if you end up finding out the film isn't any good. Or send it to Andec in Berlin, or to the Super 8 Lab in the Netherlands, much closer to you.