Only if you want to see the truck burn to the ground from the short. Get video please. You have full coverage insurance on it ? - you need it! Do not directly splice the wire in - ever!!! It will just burn up the wire and if you are lucky a fusible link elsewhere.
Your fuse is a good idea.

A better idea is your test light in place of the fuse. Disconect starter small wire. If light is on with ign in crank position you still have a short. Light on indicates a short. Again use a fuse if you think the short is fixed, but, something else is hooked up like glow plug controller etc. Fuse pops means short not fixed.
We are getting ahead of ourselves condemning ign switch when a short is present.