What are your go to monster swaps for monsters that don't exist in AS&SH.
Goblin to What?
Hobgoblin to What?
Kobold to What?
Hmmm... If you want to keep a more by-the-book Hyperborean feel, you could choose from the list below according to your HD needs, situation and locals (I do not think anything was intended to match up perfectly). In my games, I view Hyperborea as a pocket dimension, where elements from any realm, historical or fantastic, can make an appearance. The Bermuda Triangle could teleport a Nazi U-boat into Khromarium's harbor, a magical mountain blizzard could deliver a group of Samurai from Japan into the Leng Plateau, a great Mediterranean whirlpool could bring Roman sailor to the Crab Archipelago, a space-time warp could pluck the Millenium Falcon out of hyperspace to crash land in the mountains of Mt. V and so on. So, if I wanted kobolds, goblins and hobgoblins, I would import a group of them as is, perhaps banished by a powerful sorcerer's spell - it won't break anything. Anyway, there's also the list below.
Man, Bandit - HD 1 (lt 3, captain 5)
Cave-man - HD 1+1 (sub-chief 3+3, chief 5+5)
Ape-man - HD 1+2 (alpha 3+4)
Man, Wild Berserker - HD 1+4 (sub chief 3+6, chief 5+8)
Lizard-man - HD 2+1 (sub-chief 4+2, chief 6+2)
Fish-man - HD 2+2 (sub-chief 4+4, chief 7+7)
Snake-man - HD 2+2 (+one HD per class level up to 11th)
Vhuurmis (Beast-man) - HD 3+2
Crab-man - HD 3+3
Ape, Carnivorous - HD 5
As you know, the Bestiary includes Giants (Hill Giant listed as Fomorian), Gnolls (as Hyaena-men), Ogres (as Ape, Mountain), Orcs, Troglodytes and Trolls