mid '80s heads.... 2 questions

1/4" is what you want to tap those smog holes too.

When I did it on my 302 heads I just ran the appropriate drill bit for a 1/4" tap in to clean up the holes, then tapped them about half way. The drill might not even be necessary on all the holes, they're about the right size for a 1/4" tap already. Then you just loctite some allen set screws in there. If you don't thread them all the way in they can't advance to the chambers, and with the loctite they shouldn't back out.

302's didn't come out 'til '85, so those probably aren't 302 heads. The issue with the 360 heads will be getting any compression out of them. Those chambers will be big, and with a stock bottom end and stock 360 chambers you're compression ratio will end up around 7:1 unless you mill the crap out of the 360 heads.