I think a great casting choice to play OJ would have been Billy Brown. He plays Nate on How To Get Away With Murder. He has OJ's commanding presence, height, build, and deep voice. All he would need is a hair piece, and he would be good to go.
https://www.google.com/search?q=billy+brown+actor&biw=1599&bih=949&source=lnms&tbm=isch&sa=X&ved=0ahUKEwibpNnVwPLKAhXGNj4KHaFfD2sQ_AUIBigB