The elongated front fenders and the Buick grille have a lot to do with that, I think. The Muntz Jet in standard form was a very heavy, bulbous looking car. This one looks much sleeker, lower and lighter. It also has a continental kit, which sounds awful, but actually goes pretty well with the Mercury rear fenders.
The car was the subject of a restoration profile in the December '06 issue of Hemmings Classic Car. There was also a nice sidebar on Joe Bailon, who commented on the bulbous front end of the stock Muntz, which was the first thing to go.
Dan