Normal and exceptional pelts can spawn with: Oak, Werewolf, Lycanthrope
Elites cannot spawn those skills, but can spawn higher lvl skills
Such as: Fury.
I think for bases that make the most sense for metamorphasis it would be a HoW/Fury pelt for damage, and WW/Lycan/Oak for life
I'll have to go digging in arreat summit on staffmod spawns for pelts, but it's in there somewhere