Nathan, you're freaking me out, The white one is definately a Mustang GTS, i know because i bought and sold that mower in your photo (with the "bud" sticker on it) about 6 months ago. It actually cleaned up real nice.
I think the main difference between the vortex's is the blade disk, the earlier ones had a large diametre disk with about 10 upturned flaps(much like a late model 4 blade mulch and catch disk) on it with a really short set of blades. The later ones had the standard sized oval disk with a rubber/plastic skirt bolted to it to increase its diameter and give the "vortex" effect. They really are a beautiful mower to mow with but one man can only keep so many toys.
*sigh*, "oh how i miss my gold victa supreme".
