Contact Lethal Performance. They are a Ford Racing Dealer and might be able to get you a better price. Replace everything you can. Don't just do piece work. I can assure you that you will have to do the job again in the near future.
P0605 is Internal Control Module Read Only Memory (ROM) Error
P050E is Cold Start Engine Exhaust Temperature Out of Range
What mods do you have? Is it a flash tune or a hand held tuner?
I can check with a vendor that makes custom pipes. Include your name and address for shipping quote. Also the specifics of what you are looking for and I can get a price for you.
https://www.strangeengineering.net/product/rear-brake-kit-for-05-14-mustang-8-8-1-piece-rotors-dtc-30-semi-metallic-pads.html/?_gl=1*1cx39dh*_up*MQ..&gclid=EAIaIQobChMIsuiZ7fWChgMVd05HAR1IUgi9EAAYASAAEgLut_D_BwE
Why do you feel they won't work on the street? I would think a company as big as...
But codes do not tell you the specific concern. They tell you that there is a specific circuit that has an issue. Once you have the code, then you use a Workshop manual to isolate the issue.