It sounds like an expensive problem

So I got in the 2001 Tundra today, and on starting (which it did just find) there was this almighty clattering and clouds of whitish-grayish smoke from under the hood, smoke that stank of blown head gasket to me.

This truck is a working truck, has 125,000 miles on it, a lot of horse trailer towing, off-road, 4WD, and so on. I take care of it but it’s not a tool-around-town-go-to-the-grocery-store vehicle.

Please tell me I’m wrong while I wait for the tow truck and I’m very glad it did this in my driveway rather than on I-95 with two horses behind…

A head gasket shouldn’t cause an "almighty clattering " . Pick up the hood and look, could be anything from the fan hitting the radiator to a thrown rod.