Zombies without headcrabs? And Randomly Spawning zombies

[.Winnfield.]

I'm most likely to have to get an SNPC and find a way to make them respawn in a custom map, but is there another way? I want them to not have headcrabs and I'm going to use a custom skin for them, how could I use LUA to do either of these?

[JetBoom]

zombie:SetBodyGroup(0, 1)
zombie:SetBodyGroup(1, 1)
zombie:SetBodyGroup(0, 0)
zombie:SetBodyGroup(1, 0)

One of those removes the headcrab. I think it's the 3rd one.

[.Winnfield.]

Yeah buy where do I put those codes?