A method and assembly for broadcast distributing a granular agricultural material. The assembly includes a container that is configured to be supported by a chassis of a self-powered vehicle and contain a volume of a solid granular material. The assembly includes a spinner assembly that includes a first disk and a second disk that are disposed toward opposite lateral outboard sides of the vehicle. A mount arrangement is disposed between the spinner assembly and the chassis and is adjustable to manipulate a position of the first spinner and the second spinner relative to the chassis. Preferably, the mounting arrangement is configured to simultaneously adjust the position of the first spinner and the second spinner relative to the chassis.
