There's variation in the upholstery stamping between years and also on the number of holes on the backside of cargo panels for clips. I don't know which years switches were made, but one set of cargo panels with factory board is correct for my '73 body, another set has some holes offset and some that work.
Whatever you do, your best investment before install will be to use DynaMat, Cruiser Crap or any similar self-stick sound deadening mat/insulation. My doors now sound like a Mercedes when they shut and the difference inside from lining the sides, floor, firewall and tailgate is truly amazing.
For those in need, I have a set of uncut cargo panels in very good shape I'd part with. Also a template and good upholstered covers cut for speakers you could cut your own board for. PM me.