I agree with you about swapping the heads. Now is as good a time as any to do it since you already have them. If you don't have some exhaust studs laying around, it might be a good idea to get some and install them a few days before you do the head swap. Having them out on the bench where you can get to them, you can chase the threads in the heads to get them good and clean, then seal them really good and let them be sitting up for a few days while you remove the old heads and stuff. I used Teflon tape AND Permatex thread sealer on mine. They didn't leak when we ran it on the dyno, so I think they're good. Clean the combustion chambers on the heads good, with brake cleaner, screw some spark plugs in them and then get them level both ways on the bench, turned upside down with the combustion chambers facing up. Then you can pour some cheap rubbing alcohol into the chambers and leave it sit to see if any leaks past the valves. Good way to check them and see if you need to get a valve job done. I doubt they will if they were done 5K miles ago.