I dont know where you guys had trouble fitting in a 99+ mustang/cobra/mach, hell, i'm 6'5 and 290, and i find my gt to be one hell of a comfy ride. i never had the chance to sit in the drivers seat on a c5 or c6, but the c4's if it was a stick i could barley hit the clutch without getting my knee stuck under the wheel. But i would have to give up interior comfort to the gto's, roomy, seats grip decent, and great leg room.
my 2 cents, good luck on the search. Oh and 03-04 terminators ftmfw, still one of the baddest cars out, drop 2500-4000 on upgrades and enjoy the low 10 sec range.