If Aspirants Climb becomes a Brush, do you still need to score 9 points?

No — once Aspirant's Climb is replaced by a Brush token, you no longer need 9 points.

Aspirant's Climb has a passive effect that only applies while it's in play (FAQ #7987). When it's replaced by a Brush token, Aspirant's Climb leaves the battlefield, and its "Increase the points needed to win by 1" effect stops. The victory score immediately reverts to the standard 8 points (in 1v1). You only need 9 while Aspirant's Climb is actually on the board.

If you later swap the Brush back to Aspirant's Climb (via the Brush's "when you score here" trigger), the passive effect returns and the threshold goes back to 9.