My buddy (skidoohmx) on here a 780 tripple in his 97 Summit, and there are other snowesters who have triples in that chassis , that makes one powerful sled, when I went from my 97 Summit w/ 670 motor to his mod 780mod, WOW the power is awesome.
there are also some good threads on that conversion on Dootalk.com and most likely on here to , use the search.
Good Luck. Darren