building or buying? BES (HHP), TKM (Demon Performance), Hemituner Performance, American Muscle Performance, Better Built Performance. Stay away from Livernois or people that work on LS cars mainly. They are not the same. Block has to be clearanced and oil squirters have to be plugged.
Callies or Manley crank (stay away from eagle or scat), Callies, Carillo or Manley rods. Ross, Mahle or JE pistons. Thitek CNC heads are the best heads you can get. You want to use a BGE block. Better cooling jackets.
I havent built a 426 but this is being on the forums since 2006 with gen3 hemis and Ive owned 5.7s, 6.4s and have 2 hellcats.