This is the easiest, quickest way to count links
In my experience, laying an old chain side by side with a new roll doesn't work: the stretch in the old chain will cause problems with matching the links. Just count the drag links and make a new chain with the same number.
grab the old chain by a tie strap, so that all the drag links on the loop are opposite each other; "paired up". Count by two's from top to bottom.
When you get to the bottom, if they are still evenly paired, you are done. If there is an odd link out at the bottom of the loop, stop counting by two's, add the last single link, and you are done.
Do it twice if you lack confidence or practice.
To measure out cut chain: count out 10 links, fold over to make 20. Grab that 20, fold over to make 40 links. This technique can be used for almost any even number of links.
63 links? count out 15, double to 30, double that to 60, add three, mark your rivets and then break the chain. Check your length before you rivet them back together !