The technology is more along the lines of 50s-60s, with a few things here and there that step into 70s territory. But don't assume that means that we have the same vehicles and guns as real-life 50s and 60s. This is alternate history, so people who may have been needed for the creation of certain weapons may have not survived, or maybe they did but they're just farmers instead of weapons manufacturers. Or maybe they are weapon manufacturers, but their visions have changed drastically and their designs are different.
So basically, just make up guns and vehicles that fit the alternate history aesthetic, while still using 50s-60s technology.