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They have the exposed spade terminals right? Just up in where the original connector would go?
If yes, go buy some of those spade connectors from the electrical supply and crimp them onto the wires in the truck and then pop them on. If they are the right size you shouldn't have to worry about them coming loose.
If no, careful soldering of wires to the positive and negative of speaker and then connecting them to the trucks wires will do the trick. If I remember right they usually have a hole somewhere in the terminals for that purpose anyways.