You must be joking. There is no aftermarket joy for something like this. The main issue will be the fly by wire and the CANBUS in the '05 that won't work on a "normal" small block Chevy motor. This would be a custom build for you.
Just sell it and get a old pre-emissions Chevy with a 350. There you go. If you have a bad back I don't see how you would get an engine out and back in it anyway.
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