We have a few baldor dual arbor in diffent speeds, they are top notch. The current pricing on them is less than attractive though.
Also have smaller wheels rigged on a gsale 10$ motor.
From there we go down to the variable speed drill buffs with an arbor, that's as quick change as it gets with the keyless Chuck 12$ hf vsd. Used that to finish buff most of the gp100. Think the wheels are 3-4", got them from Sears locally. Used a bolt/washers/nut for the arbor.
Last but not least is the dremel buffs. They work great for tight spots. Mainly used that on al intake manifolds.