I recently came upon a 1971 Harmony H1213 Archtone acoustic. I absolutely love it, but the tuners are absolutely shot. I ordered a new set from StewMac and they fit great (spacing and screw-wise) except the posts are thicker and require larger ferrules. I'd really rather not ream the holes to accommodate the new ones and was wondering if they were even necessary?

I haven't installed the new tuners yet because I don't want to do so and then find out the ferrules are a necessity. I'm honestly a bit embarrassed that I don't know already if they're simply for aesthetics or if they really serve a purpose, but I've been out of the game for a little while and my knowledge is super rusty.

I'd really like to install these and be able to play the without having to tune after every song... ha So if anyone can give me a quick answer it'd be appreciated. Thanks!
Stew Mac has all kinds of bushings to fit most guitar tuner/hole combinations. Try them again. Look for "conversion tuner bushings", and find the ones with the right size hole. The bushings help keep the tuner shaft aligned within the headstock hole for tuning stability. Good luck.