John deere 566 pickup chain

So I'm in the process of replacing some worn out sprockets on the pickup and while in there said may as well do new chains too. Doesn't make sense not to start fresh. My problem is that when I went to install the chain with calls for 42 links including the master it was too tight to put the master link in. The old chain was really loose. (probably a combo of worn sprockets and stretched chain)

The tech manual says to loosen the bearing bolts and pry the chain tight. But in my reading online it says to only do that if the chain is loose. So my question is what do I do to get the chain to fit? Can I use a half link? Is there a way to do this correctly?