I originally wanted a Cobra but bought a Mach 1 instead because it was about $5-7k cheaper. I now have about $20,500 invested in my Mach 1. This includes a complete 03-04 Cobra eaton setup, fuel system and T-56. Car put down 440/405 with nothing but a Stage 1 port, CAI, and exhaust (stock pulleys). I'm rods (which I have) and pistons away from having everything a Cobra would have but with the lighter alum block and a solid axle.
BTW, Mach 1 interior > Cobra interior , in my opinion...