Dia-Compe and Weinmann brakes of the 60s-70s are pretty indistinguishable. I think the former had one more loop of spring steel on the centerpulls. The levers are completely interchangeable. Dia-Compe held the patent on the "extension levers" (aka turkey wings etc). Cooperation between the two companies goes back to the early sixties.
Not exactly the case. Weinmann has a guide between the two arms that seems to help a lot with keeping the brakes centered, Dia Compe does not. It is true that the DC's have an extra loop in the return spring, it gives them a lighter action than the Weinmann's.
You should consider having a quick release on those brakes, so if you do not have a release on the cable stops then get brake levers with a built in release. Both DC and Weinmann offered brakes with either setup.