Rare 1969 Mustang Boss 429 Prototype Under the Hammer.

When it comes to classic Mustangs, collectors can choose from a comprehensive list that includes ponies such as the Shelby GT350, GT350H, GT500 or the Mustang Boss 302 and the Mach 1.

There's also the very Cobra Jet and the Boss 429, the latter having no less than 375 horsepower at its disposal. We've seen one of these 429 models cross the block for more than a half a million dollars last year. It was original and unrestored, and had only 902 miles on its odometer. A fantastic piece of musclecar history.

Now we're back on the matter to report that another Boss 429 is getting ready to change owners under the hammer. This time we're talking about something a bit different - one of the first 50 hand-built 429 prototypes.

Specifically, it's the 38th such vehicle constructed by Ford and it's the first Candyapple Red Boss 429 built and sold. Another reason that will make it appealing to customers is the fact that the scooped hood hides an 820-S NASCAR engine. And that's because this vehicle was built and tuned to compete in the NASCAR Grand National Division (today's Sprint Cup).

Since only the first 15 vehicles were used as test cars, the Candyapple Red Boss 429 is the 23rd model offered to the public. Considering its specifications and rarity, it should fetch no less than six figures. The musclecar will be auctioned off during Mecum's Kansas City Spring 2014 event between April 24-26.

Hand-built 1969 Ford Mustang Boss 429 highlights:
- The first Candyapple Red Boss 429 Built and Sold
- KK #1238, the 38th Boss 429
- One of the first 50 hand-built prototypes
- Early 820-S NASCAR engine
- Complete ownership history
- Original build sheet
- Rotisserie restoration completed in 2009 by Randy Roberts of Muscle Car Restorations, Inc
- Final detailed markings by Boss expert, Ed Meyer
- Listed in and verified by the New Mustang Boss Registry
- The first 15 were test cars so this the 23rd car offered to the public.