You can just go back on using your existing game. Make sure you finish first or second (min) in each race and watich out for Lei Bing (I think that's her name?). It's often a good idea to try to take her out in later races because she seems to win everything. Good luck!
100% Arcade = 29 + 6 Hasbro games (1st to post complete: Speedball 2)
100% Retail = 134 (2nd to post complete: Flatout: Ultimate Carnage & Monster Jam 07)