I was a Launcher operator for a nuclear warhead missile during my time in the Army, the Pershing Missile. I'm not sure what you have in mind, but this was a two-stage missile, but it was still just a 3' diameter, 35' long pointed tube. The interesting part of the system was the tracked vehicles the missile system was mounted on. They were blown Chrysler powered versions of the Army Personal Carrier with aluminum bodies and configured more like a pickup to carry the modules for the missile system.
Yeah, I've done a conversion:
This is one setup in firing position, but it had been gregariously painted for show. The real ones were OD with flat black warhead.
Nuclear warheads were not fired off a low range missiles, ie. small. The Pershing was based off the Redstone Missile that put satellites into space. You DON'T want to drop one of these rounds anywhere close to you! The warhead itself looked like any other conventional warhead. There's nothing of any external difference to distinguish it. In our case, during the 60's, we used dummy warheads to practice and the real ones were painted flat black as opposed to olive drab everything else. Also, the vehicles in out unit had NO typical markings, just a single battery number and a colored dot on the bumpers ... my battery had a red dot. That was like driving around with NO license plates.
Hope this gives you something to think on. Let me know if any of this is in line with you're looking for and I can dig out the unclassified photos.