I have an extra 350 block that i was going to use in a project. I just noticed that it has a crack in the block right under the head down by the plugs. Is this something worth trying to fix or no?

No.

you could try a host of different repairs, and some may even work, but starting with a crappy block will always be in the back of your mind. You also don't know if there are other cracks lurking elsewhere.

Is it in the head of block? It sounds like you are describing the head. If its the head then just get another set. If its the block get another block. Im sure there are hundreds of them out there for a good price.