minecraft-assets/data/minecraft/worldgen/configured_feature/trees_old_growth_pine_taiga.json

{
  "type": "minecraft:random_selector",
  "config": {
    "default": "minecraft:spruce_checked",
    "features": [
      {
        "chance": 0.025641026,
        "feature": "minecraft:mega_spruce_checked"
      },
      {
        "chance": 0.30769232,
        "feature": "minecraft:mega_pine_checked"
      },
      {
        "chance": 0.33333334,
        "feature": "minecraft:pine_checked"
      }
    ]
  }
}