Fellow tabletop nerds, how would you stat Tyranids for D&D 5e?

I'm running a one-off for my brother's birthday and I had a moment of inspiration to use my Tyranid models as the bad guys since I don't have a ton of monster models right now.

So how would you stat rank and file Tyranid models for a level 5 party in 5e? They don't have to remain completely faithful to 40k lore, I'm mostly looking to build stats based off of combat roles and what the model looks like. I'm planning to use Gaunts, Genestealers, Raveners, Warriors, a Lictor, a Hive Guard, and a Melee Carnifex. (Maybe Gargoyles, too)

Are they Aberrations, Beasts, Monstrosities, or Other?
What abilities should they have?
About where do you think they should fall on the CR scale? (I'm thinking Gaunts should be 1 or 2, and Warriors at 4 or 5)
Any other thoughts?

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Thanks for any help!