Do I need these? (i have no idea what they are called)

[karmakaze]

Do I "need" these? Or are the just to help align the head on the block?

(that is not my block by the way, just a picture i found)

[Hijacker]

I'd say yes. They're guide pins to make sure your head and gasket are all even before you start torquing bolts down.

If you're missing them, or they got damaged, I think Nissan just uses the same guides for most of their motors. So you should be able to get some for a KA and have them work. Or out of a Sentra just to be on the safe side.

BTW, that is one clean block and I am jealous. Just got my block back from the shop from being hot tanked, and it still looks dirty.