For me, the perfect combo is the White streak and the GL-40.
But I do know that it might not suit everyone, but this is my build. But if you really think that you want to change the weapons I do think you could go with shotguns too.
"But how do I mod them?", I'm glad you're interested, but I think that you can mod it pretty much as you want. With the GL-40 you should go for max concealment, no need for boosts. And with the White streak, I do think that as long as you have above 180 damage you're fine, but it wouldn't do any harm to invest in some accuracy mods.