J74 and J75 are both d'addario string sets. No one I know (including me) changes their strings frequently enough. If you've never changed the strings on this and you've owned it for 3 months or longer it doesn't matter what strings you get - they will sound way better than what's on there now. You need loop end strings with the standard Eastman tailpiece. Change your strings one pair at a time. Loosen all strings down 1/2 step first. If you take all the strings off an archtop instrument the bridge will come off, giving you valuable practice in setting the intonation. Do you know how to work the tailpiece? The cover should slide off toward the endpin to give you access to the string loops. Pay attention to how they go thru the hooks, especially the A and E strings.
Your Eastman mando already has a bone nut - changing it out with antler or bone will only impact your wallet.
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