Ran across this today thanks to Luis. M22 out of a supposed LS6 according to the current owner but could be an LS5 as well. I did not find anything about the car in my database or an internet search but in case anyone has any info, the transmission is stamped with 10K141329 so a mid to late December built 454 Chevelle.
https://bend.craigslist.org/pts/6020308271.html