For the 1960s, since they don't make many good airsoft lever guns, try to find one of those M40 sniper rifles and make it look like a convincing Remington 700.
As for handgun, buy a spring Marui M1911A1. And of course the clip/magazine terminology is questionable.
For the 90s use a Colt Python, they make a decent airsoft revolver for that.
For the 2000s, pick whatever works.