A gt2876r is a weird turbo and I would not recommend it. The compressor wheel is too big for the turbine wheel. A gt2871 would get you to 300whp very easily and would offer tons of transient response. 300whp for a gt3071 is child's play and would spool a little slower, but if you're never below 3500, it wouldn't be a problem. It's a tough call because both turbos would work for what you want. Really, if you flipped a coin and chose one, you wouldn't be worse off. I would say if you were doing AutoX, gt2871, but you said you're doing road course.
Also, it's "wastegate"