A turbocharged, all-wheel-drive Honda Civic masquerading as a Subaru WRC car; an open-wheel MG Midget built by college kids; and a Pontiac Sunbird clicking off 10-second quarter-mile times: They can all be found together in only one place, the Grassroots Motorsports $2014 Challenge. The event meets every year at Auto-Plus Raceway in Gainesville, Florida, seeking the finest and fastest cars …