Although Michael Ansara was Cochise throughout the run of the TV series version of 'Broken Arrow', Ricardo Montalban played the part in a one hour adaptation of the movie. This was presented as an episode of 'The 20th Century Fox Hour', which usually made TV versions of the big movies from that studio.
John Lupton also appeared in this version of 'Broken Arrow' as Tom Jeffords, the character he would then later play in the series. So, either this took place in an alternate universe in which Cochise had different DNA than his counterpart, or we should employ any one of a number of splainins for a character to be replaced temporarily - although I think we can rule out plastic surgery and a fraternal twin brother. (Had Montalban been the actual Cochise and Ansara the doppleganger, that replacement would have been permanent.)
And then there's alien impersonation. It may seem really out there, but that's the one I'm leaning towards.....
It's already an established Toobworld theory that Mr. Roarke of 'Fantasy Island' was a Gallifreyan Time Lord. In the original series, we learned that he was over 300 years old. And in the remake, we not only saw that he had been regenerated, but that an old shack on the island was a TARDIS. It's also part of that theory that Roarke was once a renegade Time Lord as well, submitting to the Dark Side under the human name of Ramon Castillo (as seen in an episode of 'Zorro'.) And for Toobworld's purposes, there is a theory of relateeveety that claims Castillo was the biological father of Miquelito Quixote Loveless.
So I'm thinking that since he was around at that time anyway, Roarke had reason to impersonate Cochise. There is always the quesiton of what was done with the original Apache warrior during that period, so we could say that Roarke used his own version of a quantum leap accelerator on board his TARDIS to go back in Time to replace Cochise bodily. And the real Cochise would be left inside the "waiting room" of the TARDIS.
Roarke probably did this in order to insure that the alliance between Jeffords and Cochise did take place. Even in its unembellished historical version, so much could have gone wrong.
At least if he was impersonated by a Gallifreyan, we don't have to study the recently restored copy of this TV episode to see if the alien Cochise had a pinky finger bent out of shape.......
It's not an air-tight case, but that's my story and I'm sticking to it.