He didn't say what year the TransAm was, but unless it's from the late 90's, I doubt it will have galvanized sheet metal, will it? Seems like that was a fairly recent developement for American cars, even tho high end European cars have had it since the mid- 70's....
But your point is valid, especially for newer cars, where the primer coats are electrostatic or immersion processes.
But if he's doing a true restoration all the way down to the last nut and bolt, I still don't see the point of sanding all the paint off, that's a lot of work that will go much faster and better using strippers and/or sandblasting.
But to answer the OP's question, for quick removal what you want is an angle grinder, and use either sand paper or a wire brush. The point is simply to get it off - quickly......