I have a 2014 Mustang GT with 4-piston Brembos (with cooling ducts) and I have great success with these pads:
https://www.powerstop.com/product/track-day-brake-pads/#y=2018&mk=FORD&mo=MUSTANG&ss=Shelby GT350; Shelby GT350R;
These are the pads for your GT350
https://www.powerstop.com/product/track-day-brake-pads/#y=2018&mk=FORD&mo=MUSTANG&ss=Shelby GT350; Shelby GT350R;
The only downside is they are dusty as hell and if you run in the rain, the combo of water and heat results in concrete-like deposits on the wheels. Better have them coated.
The pads are about 1/2 the price of GLOCS or CarboTech. I run their Ceramic-Metallic Z26 pads on the street and the pad compounds are compatible with each other.
I am SO GLAD you posted this! I ran the Raybestos pads for the first time on my GT350 at Charlotte in the rain and when I got home I had these concrete deposits in the nook on every spoke of my front rims. The Raybestos worked great on track but I had to buy a gallon of Sonax and spent three evenings scrubbing my wheels to get the tarter-like concrete off. I've used several different pads on my other cars and never seen the buildup this bad.
Do other pads have this?