Instead of slapping a charger on them, at whatever state of charge that they are in, I would load each battery at 5 to 10 amps until it read 12.0 ish voltage under that load, than apply 20+ amps until 14.7v is reached, then hold until amps taper to 0.66a or so.
Let rest 24 hours, check voltage.
Draining the battery to ~50% then applying a higher charge rate for longer could be more effective than simply trying to top them up from where they now are.
My Northstar AGM always responds much better after a high amp recharge from its most depleted state. I'll intentionally discharge it to 50%, or below, when I noticed performance sag, so I can give it 40 amps for longer before it attains absorption voltage.
After the high amp recharge, subsequent full recharges, when I hold 14.7v until amps taper to 0.45 or less, take less time.
The Northstar is a TPPL(thin plate pure lead) with no upper amperage limitations. Your Fiamms are designed different for a different purpose, but I would still not be afraid to feed them 30% of their rated capacity. But the two in the 12.6v range will not acccept this much current for more than a few seconds before attaining absorption voltage. Which is why my opinion is to discharge them to ~50% then feed them upto 30%, 30 amps per 100Ah of capacity, until 14.7v is reached and hold 14.7 until amps taper to 0.5% of capacity.
After doing that then one can better judge their condition, and the initial discharge to 50% can also give indications as to their health, and yield a yardstick for later comparison to see if the conditioning had any effect.
