Tow Vehicles - Warranties - Suspension Lifts

Hope this is not too off topic (as I need a tow vehicle to get the boat to the water) but has anyone had a good experience with any extended warranty companies?

Specifically those that have tow vehicles with lift kits/oversize tires, does your warranty cover you?

I am seeing that most warranties (and extended warranties) are null and void with such modifications so it would seem pointless to buy one or place a value on any manufacturer's warranty still left on the truck.

Thanks,
Chaun