I think there's an implied double-question here:
- Could a killed Clone Trooper be used as spare part for a wounded one?
- Would a killed Clone Trooper be used as spare part for a wounded one?
And, as shown above, the answer to the 2nd is "No." It's not cost effective for them to do that. While some Jedi show compassion for clones, some don't, and in terms of cost, speed, and battle-readiness, this is impractical.
But as a direct answer, yes, they could be used as a replacement, since they match genetically, have the same blood type, and so on. We can do it with our tech, so there would be no reason they couldn't do it. (I suspect most of the time there's no real reason, since clones are cannon fodder, but they might find it worthwhile if it were an extremely experienced commander who's life could be saved.)
I tried searching the Wookieepedia for anything about clones and transplants. The only reference I found was that cloning was expensive and outlawed after the Clone Wars, leading to the use of cybernetics instead of cloning. (But that doesn't provide an instance of transplants for clone troopers.) (I searched using Google and the Wookieepedia search functions for combinations of the words clone and transplant, as well as a few others like replacement, organ, and limb.)
While I can't cite an example of this having been done, I can't find any examples of it anywhere in the Wookieepedia.