The Boss is... Boss

Motortend just ran a Ford Mustang Boss 302 on the Laguna Seca track.  Best lap time was 1:40.21... which beat Nissan GT-R, Audi R8 4.2, BMW M3, Cadillac CTS-V, and Ford's own Shelby GT500.  

From www.fastlaps.com:

10.	Ford Mustang Boss 302	1:40.21	129	'12	446 / 1659	Motor Trend
11.	Nissan GT-R	1:40.45	129	'08	479 / 1740	Motor Trend
12.	Mercedes SLS AMG	1:40.74	129	'10	571 / 1620	Bern Schneider
13.	Audi R8 4.2 FSI quattro	1:40.75	129	'06	420 / 1560	Motor Trend
14.	Chevrolet Corvette Z06	1:40.90	129	'05	513 / 1437	Motor Trend
15.	BMW M3 (E92)	1:42.96	126	'07	420 / 1619	Motor Trend
16.	Porsche Cayman S(facelift) PDK	1:43.00	126	'08	320 / 1375	Motor Trend
17.	Porsche Cayman S	1:43.00	126	'05	295 / 1406	Randy Pobst
18.	Aston Martin V12 Vantage	1:43.04	126	'09	517 / 1680	road&track
19.	Cadillac CTS-V	1:43.90	125	'09	564 / 1955	Motortrend
20.	Shelby GT500	1:44.30	124	'10	547 / 1767	Motortrend
21.	Shelby GT500	1:44.72	124	'06	507 / 1807	Motor Trend
22.	Shelby Mustang Cobra GT500KR	1:44.72	124	'08	540 / 1773	Motortrend
23.	Porsche 997 Carrera (2008 facelift)	1:45.00	123	'08	345 / 1415	Car and Driver
24.	Jaguar XFR	1:45.37	123	'09	510 / 1960	Motortrend
25.	Chevrolet Camaro SS 2010	1:45.70	123	'10	432 / 1750	Motor Trend

Neat video here.