Gene, from Hull Kingston Rovers, will line up for his third successive World Cup having played in 1995 and 2000, while it will be the first time for the former Queensland Origin representative Costigan.
Kumuls coach Adrian Lam named 27 PNG residents in the squad along with 22 overseas-based players, including four current NRL players and three UK Super League players.
The final team of 24 will be named on October 8.
The squad includes the nucleus of the team that drew 24-all with Australia's Prime Minister's XIII in October last year.
Townsville, in Australia's north, will be the Kumuls' home during the tournament in its strong pool against Australia, New Zealand and England.
The Kumuls open their campaign against England in the first match of the 2008 tournament in Townsville on October 25 before playing New Zealand on the Gold Coast on November 1 and then returning to Townsville to play Australia in November 9.
Squad: Paul Aiton (Panthers) Macali Aizu (Hull KR) Jay Aston (Storm) Michael Bani (Sea Eagles) Wayne Bond (Redcliffe) Tom Butterfield (Brisbane) Richard Cambo (Wentworthville) Jason Chan (Windsor) Neville Costigan (Raiders) Trevor Exton (Ipswich) Steve Franciscus (Banyo Brisbane) Stanley Gene (Hull KR) Rod Griffin (Northern Pride Cairns) Sam Joe (Storm) George Keppa (Brisbane North) Tuu Maori (Roosters) David Moore (Titans) James Nightingale (Windsor) Merv O'Flanagan (Souths Logan) Keith Peters (Panthers) Kevin Prior (Wentworthville) John Wilshere (Salford) Dion Aiya (Bingtangor Eagles) Dominic Angra (Bingtangor Eagles) Sigfred Gragande (Bingtangor Lahanis) Nigel Hukula (Bingtangor Lahanis) Jessie Joe (Masta Mark Rangers) Benjamin John (Masta Mark Rangers) Gimapau Keimelo (Masta Mark Rangers) Geno Kima (Agmark Guiras) Nickson Kolo (Masta Mark Rangers) Anton Kui (Bingtangor Lahanis) Larsen Marabe (Agmark Guiras) Michael Mark (Masta Mark Rangers) Mark Mexico (Toyota Mioks) George Moni (Mabey & Johnson Muruks) Thomas Ninkama (NCD Civpac Vipers) Joseph Omai (Mabey & Johnson Muruks) Charles Onguglo (Masta Mark Rangers) Benny Pamunda (Bingtangor Eagles) Kingston Pisep (LBC Bombers) Rodney Pora (Mabey & Johnson Muruks) Francis Ray (Bingtangor Eagles) Elizah Riyong (NCD Civpac Vipers) Rodney Ropra (Mabey & Johnson Muruks) Niko Ubile (Bingtangor Lahanis) Charlie Wabo (Mabey & Johnson Muruks) Menzie Yere (Agmark Guiras) Simon Young (Mabey & Johnson Muruks)