You don't need a block breather. It's only their to free up a little HP by partially evacuating the block.

If you don't care about that little perf boost, then just use the valve cover breather, the blowby can push past the pushrods and get out the top eventually.

It's also used to postively ventilate the block using a metered amount of fresh air. You don't need it, a little condensation might form without it but it'll take weeks to cause a problem. Just change your oil regularly.