The guy to ask would be Richard So
He is the ADS refurb guru
https://www.adsspeakersservice.com/
ADS speakers still have something special to the sound and they still hold up even to this day.
I have owned L1590, L1290 and L710. All in super awesome condition physically. Mine sounded good as is but I always sent all the drivers and crossovers off to Richard So. He uses new old stock parts in the crossover but they weren't what I would call high end. He isn't really interested in modifying the crossovers. He does what he does and that is it.
I always enjoyed the soft down tweeter and ease the speakers played with. I ended up selling my last set a couple of years ago and I am ADS free for the first time since the mid 80s. I do miss them.
One thing that I will say is that while they sound good in a nostalgic kind of way, when you compare them to modern speakers they fall short. But I loved playing vinyl with my modified Yamaha CR-1020 and whatever ADS I had at the time. That system in itself was sort of a time machine.
I highly recommend Richard So and do it sooner than later as he is finally getting low on some of the new old stock.
By the way, Richard So worked for ADS for years. At some point long ago he bought all there new old stock. He has been around for a long time and is one of the few that know exactly what he is doing when updating them to newer parts. You don't get anymore authentic ADS work than Richard.