I'm going to press and pin the barrel. I have one of the virgin Yugo trunnions, which should make it easy.
If I was having to start with a threaded trunnion I'd probably bore it smooth and pin it.
Timing the gas ports on a threaded setup isn't all that bad - just torque the barrel in place a few times to make sure the threads are all mated up, put a witness mark on, and then line up on that - but press and pin is way easier. It's one of the things I expressly like about the AK.
Using a pressed trunnion that already has a pin hole makes things a lot harder. The most reasonable solution for that is to thread the trunnion. wttool.com has the proper tap for $30-ish, which is amazingly cheap, but tapping hard steel like a trunnion can be iffy. If you cut internal threads on the lathe, you might want to press a sacrificial pin in first, bore it flush with the ID, and then thread across is. The threading tool will tend to deflect going across the interruption of the empty pin slot, which can cause troubles, particularly with a light duty lathe like mine.
Hmm... looking at my Yugo trunnion while I'm typing this, I just had another idea. Back in the main AK section I posted some pictures of stamped Valmets; one of them used a rivet instead of a plain barrel pin, since the Valmet's upswept receiver front is missing the place where the lower rivet would go. So they made the barrel pin take the place of the lower rivet.
It looks like there's room to open up the lower-front rivet hole in the Yugo trunnion. You'd have to offset it up a bit. For a garage shop, you could carefully egg the hole up with a carbide burr in a Dremel until it intersects the barrel, then make the hole round with a drill and reamer.
Again, while drilling and reaming, a piece of scrap steel or old barrel stub pressed into the trunnion would help a lot. Ideally the hardness should be the same as the trunnion to keep the bits from wandering, but even softer metal would be better than nothing.
Then just rivet the front of the trunnion as usual.