Well a 268 is pretty big for a teener, and it's gonna want some bypass air alrightee.
Ok so first things first get a PCV and grommet plumbed in there and a decent breather on the other side. There's nothing wrong with the oiled filter you have on there now, except a few hours after installing it on a running engine, the oil will have all been sucked out of it, and the filter will now start to pass dirt. And whenever you go WOT, blowby will flow backwards through the filter and puke oil-mist all over your valve cover,and then the dirt will stick to that. So, if the breather on the passenger side passes air in both directions then use it and shelf that little one on the passenger side. Ideally the new breather should be plumbed to inside the filter house,between the filter and the air-horn. I know, I know , that's a PITA. So What you can do is install an exit hose on the breather nipple about a foot long and point it anywhere except down.Then the blowby will mostly leave it's oil in the filter or in the hose where it can drain back. But make sure both access points in the covers are baffled inside. The breather will require maintenance.
After this,the engine will require a retune.