The painted steel valve covers are the same for 1970 and 71 for 4bbl and 6-bbl. It pretty much depends on whether they have the spark plug wire and wiring harness tabs on them in the right places.
Here's something I found real quick that breaks it down with photos:
https://board.moparts.org/ubbthreads...ate-dates.html
AMD makes a really nice set of reproduction steel valve covers:
https://www.autometaldirect.com/amd-...406-p-662.html