Race pandering will HURT, not help Trump and neither of the choices you mentioned would 1) bring in never Trumpers 2) more black votes 3) and might just lose some GOPer votes. 100%
But if Trump is going to shamelessly pander, he needs to shamelessly pander to Latinos, not blacks. That's where the votes are.
I don't care what race or ethnicity ( except NO MUSLIMS of ANY ethnicity! ) Trump picks; however, I do very much care about WHO that person is re qualifications and what that person adds to the ticket.
And to some extent, so does age now.