There are any number of mods to this car that I don't agree with, but it all comes down to personal opinion so I don't rag about it too much. However, IMO, Mopars are popular enough with enough aftermarket support to keep engines family to family. Its not like they are an orphaned brand with no aftermarket support and new mills available out there like a Studebaker. Sure, the OEM tech is not as aftermarket friendly as the GM stuff, but it can still be adapted with a little bit of effort. Similar to late model GM stuff, late model mopar stuff is highly efficient and can make easy power. I can't say there is any defining reason to put LS power in a Challenger.
I have checked out the site of the garage that built this car, and they put LS into everything they build, even the two Mustangs they have, so I guess originality isn't their forte