The What if the prequels were made in the 80s? podcast/video was a fun project to listen to, with some great calls for the casting.
So in a similar vein for this, I’d go with:
Old Han - Robert Forster
Old Leia - Debbie Reynolds (once I saw Morgan suggesting her I can’t now think of anyon eelse!)
Old Luke - Bill Bixby
Rey - Jami Gertz (maybe Jennifer Connelly if not too young for the role?)
Finn - Mario Van Peebles
Poe - Judd Nelson
Ben Solo - Kiefer (great shout by Morgan)