Fixing door sag. with frame rail connectors?

My 66 cuda has a very slight door sag, so slight in fact that you can't see it. I just notice it because when I set my F.A> in the car the door doesn't close properly unless I slam it.

I was looking at seymour_scamps frame connectors and getting ready to order a set thinking it would fix my problem if properly installed. If I support the car under the frame on jack stands the problem is not present. Will this work or not?

OPINIONS?

TIA Vern