Far as I know, the Elkys had car motor stampings. Plus, the three character code (CXX, TXX) began in 1970. Finally the L 5 70 would have been a 5th week of December 1970 date, which makes it right for a 1971 model year motor.
So, it may have been in a 69 Elky at one time, but it's a 71 truck 402. You'd have to pull a valve cover to see if the 402 heads are still on it, and I can't remember if 71 heads would have been open or closed chamber. I can check the book and let you know tomorrow if it matters...
Nothing wrong with a 402 (as written by the guy who found out his 350 horse 396 that came with his 69 Camaro was really a TLM coded 72 402).
Joe, glad to see I'm not the only East Coaster still here....
69 'vert project big block/TKO 600 RR
68 'vert driver RS clone -- gone!