The easiest thing, I think, is going to be the camo. Go with an overall tan or the NATO 3 color.
After that, you can do some structural changes that would do the trick. First of all, I'd replace the missile nose cone with something more like a Pluton or ATACMS. Next, I'd do something with the fins. At least cut them down to be small like a Pershing II. Alternatively, make the flip out or just eliminate them altogether.
Next (and a relatively simple change), I'd look at armored shutters on the windows, like the MLRS or HIMARS. That shouldn't be too hard and should really change the appearance. You may also want to make the right windshield vertical or sloped slightly back just to change the profile. The forward-angled windshield isn't too common in the West (not as common as Soviet bloc large trucks).
Other ideas that would make it seem less Soviet, but are more difficult:
New tires. Some wheels more like a Oshkosh product. Western tires have totally different treads, usually blockier. The tires themselves also have more vertical walls, typically.
Finally, the most extensive change you can do to "Westernize" the Scud is to hid the missile. A lot of Western designs put the missile in a box, like the Pluton, ATMOS, Patriot, or MLRS. Soviets generally exposed it or put it in a tube or leave it exposed (the look cooler in May Day parades).
Cheers,
Logan
