Bunched in one group, Reyes, the former world 9-ball champion, and Bustamante, the former world No. 1, needed a pair of victories over Fil-Am Santos Sambajon to pull it through the tough bracket, finishing with identical three wins and assuring themselves of $30,000 (about P1.5 million) each.
Four players actually wound up with three wins in Group 74, with Bustamante and Gabriel Owen of the US gaining outright berths in the next round and Reyes nipping Ivica Putnik in the tiebreak to advance.
Ronnie Alcano also made it past a tough group that included former world 9-ball titlist Thorsten Hohmann and topnotcher Quinten Hann, scoring three wins and edging Dee Adkins for the third and last berth.
But it was in Group 76 where the Filipino cue masters struck hardest as Alex Pagulayan, the world 9-ball champion in 2004, Dennis Orcollo and Rodolfo Luat all advanced with three wins apiece, beating the likes of veteran campaigners Mika Immonen of Finland and Niels Fiejen of the Netherlands.
Marlon Manalo, on the other hand, produced the worthiest win among the Filipino bets when he topped Group 75 with four victories to lead the six-player cast in round 5 that includes Pagulayan, Hohmann, Owen, Swede Marcus Chamat and Scot Rico Diks.
Bustamante, Orcollo and Alcano are grouped with German Ralf Souquet, American David Matlock and Daryl Peach of Great Britain.
Reyes and Luat banner the Group 79 field that includes 8-ball stalwarts Evgeny Stalev, Larry Nevel, Darren Appleton of Great Britain and Hann.
Only the top two players in each group will advance to the final round, another round robin phase among the last six players with the winner getting the top $350,000 purse.
Among the previous nine Filipino survivors, only Sambajon and Antonio Lining failed to advance to the fifth round. Both players swept their assignments in the third and fourth rounds, respectively.