I would take a guess that the carpet from a Lancer or similar sized FWD car would be close to fitting the profile of the truck floor due to the shallow transmission tunnel. It will probably have holes and overhang that would need to be dealt with somehow, but if your trucks' carpet is thrashed or it's only the vinyl floor you should be able to pick something up from a yard cheap (if you can handle the process of stripping out seats and centre consoles etc to get to it...)