A division commander, which Clark was at that time, cannot do that on his own. First, the DOG or whoever must make the request. Then there is a Congressionally mandated procedure for providing military equipment to civil law enforcement that requires high level Army involvement. If approved, the closest Army installation with the requested equipment is tasked to provide it. In the Waco case, it was Fort Hood, TX. The III Corps commanded by LTG Funk would then have designated either the 1st Cav commanded by MG Clark or the 2d Armor commanded by MG Bates (I think--the names are starting to run together on me!) to provide the Bradleys & Combat Engineer Vehicles that were used at Waco--no crews, BTW--equipment only.
In any event, even though Clark has many faults, Waco was not one of them.