Above images are from http://www.letsmow.com and this blog is titled, The Cutting Edge. Pretty cool!
Learned about it from the event calendar on http://www.goldeagle.com/event_marketing/engine-answerman-tour.aspx and also borrowed the bottom photo to show you what a Monster Truck treatment does to a lawn mower
FYI, the worlds fastest lawnmower is claimed by the Dixie Chopper Jet Mower built in 1991 by Dixie Choppers owner Art Evans and was on a 1993 episode of Tim Alllen's sitcom Home Improvement. The fastest at Bonneville is the black one above (not the monster truck one) which clocked at 96.529 in 2010