Suzuki 2 Strokes

Ok, Im looking at the newer wheels on bikes like the katana, GSXR and so on. Will any of these bolt onto the older bikes?

You need to consider diameter, width and of course if you plan on updating to a rear disc since the wheels you are after all use one. The 380 cant take too wide a rear tyre or front either so your choices are again limited if you keep the stock forks and swingarm.
Early 80s snowflake style GS cast wheels can fit in with some minor updates, the front being an almost direct drop in from some of the 450 and 550 models.
The GS450 used a rear drum if I remember correctly, but be aware of the LTD model types of rear drum wheels as they are all 16 inchers.

What does it take to put a 80s or 90s katana rear swingarm into a Gt380?

You will need to get the following info from your bike:
Swing arm pivot width
Swing arm pivot centre to axle centre (set in centre of adjuster slot)
Pivot and axle diameter
Distance between the faces of the swing arm at the axle
Once you have these measurments you will have to go to your wreckers yard and look for models of aluminum swing arms with twin shock mounting that are the same as or very close to your dimensions.
The axles can be up-sized somewhat if you're changing the wheels but keep all of what you are doing in mind and possibly all parts from the same brand of bike.
This way if you find a swingarm from brand A the wheel for brand A for that swingarm makes your life a lot easier to fit it in.