You can go here to find a full list of what monsters spawn where in the Guiding Lands. Once you get to MR69 and remove your MR cap again you'll have full access to all T2 monsters in the Guiding Lands. Spiritvein Solidbones are available once you get to MR49, complete the assigned quest to remove your MR cap and then level up biomes to level 5 so that some of the T2 monsters start spawning.
Spiritvein Slogbones are available for farming once you leveled up a biome in the Guiding Lands to level 4 so that T1 monsters start spawning. You'll also be able to eventually get more T1/T2 investigations in the Guiding Lands. You can either gather tracks/break parts in other hunter's T1/T2 quests online or from one of the T1/T2 optional quests (e.g. If you've completed the main story then, once that MR cap has been removed, your MR will likely be high enough that you'll able to farm T1/T2 investigations. In terms of actually being able to pursue these methods you're going to need to hit certain Master Rank (MR) requirements.
Melding Spiritvein Solidbones from GL T2 monstersĮvent Quests: Supply Cache Tempered Elders Melding Spiritvein Slogbones from GL T1 monstersĮvent Quest: 'The Wrath of Thunder Descends'
