This is what I see on the calendar for August:
(Best bet for a Cobra and your expressed interest... Road America with the Northwoods Cobra Club 8/5 & 6 Looks like it could fit in nicely with your schedule. NASA has Cobras in wheel to wheel racing and certainly in HPDE but that's in Ohio.)
Sat. & Sun. August 5-6 Road America (Northwood’s Cobra Club) – HPDE
http://www.nwshelbyclub.com/
Sat. & Sun. August 5-6 Waterford Hills (Audi Club) – HPDE
http://www.audiclubna.org/
Fri. & Sat. August 11-12 Blackhawk Farms (Audi Club) – HPDE
http://www.audiclubna.org/
Sat. & Sun. August 12-13 Mid-Ohio (NASA Midwest and IN/OH) – HPDE
http://www.nasamidwest.com/
Mon. August 14 Gingerman (CGI Motorsports) – HPDE
http://www.cgimotorsports.com/
Sat. August 19 Gateway International Raceway (Audi Club) – HPDE
http://www.audiclubna.org/
Sat. August 26 Blackhawk Farms (Midwest Council) – High Speed Autocross
http://autocross.mcscc.org/events/schedule.php\
Mon. August 28 Gingerman (CGI Motorsports) – HPDE
http://www.cgimotorsports.com/