I did a similar purchase 4 years ago when I bought 4 T105 from a local Trojan distributor here in Phoenix. I was charged $25 each for 2 year old batteries removed from local golf resort golf carts that were under contract with this distributor for new batteries every 2 years. Before he would release the batteries to me, he needed several days to charge and test and assess equality of the set. All came from a same date code group and are still in use in my coach. I went this route because I was adding for a total of 6 batteries and wanted all to be about same age. Of course the price was right too.
On a yearly basis I check the batteries using my microwave oven as a load while operating off of my inverter.
In preparation, check water and adjust, then fully charge the total battery pack(6 batt. in parallel). Let them sit a day then run an equalization cycle. This may last more then 8 hours. Near the end of the equalization and while it is still passing a charge current, I check voltage with DVM of each 6 volt battery. They should all read within 20mv.
Top off the water in each cell
I now use the microwave oven to heat several qts. of water to boiling. I repeat this process many times. This puts a 150 amp load on my total battery pack. Or 50amps from each of the 3 banks. I repeat this with more cold water until I come close to the 50% discharge level of the amp hours of the total battery pack. (About 2 hours worth of water heating). While the last load cycle is still running I use a DVM to check voltage across each 6 volt battery. They usually measure within 10-20 mv under load. If every thing is ok, I let the batteries sit for several hours with no load. Check the state of charge voltage and see how close it falls to the 50% SOC at the current ambient temp.
2003 34' Dolphin 5342, W22, UP, UPGBrake, F and R Track Bars, Rear IPD sway bar, Koni FSDs, Safe-T-Plus, Scan Gauge II.. 2004 Jeep Liberty, Blue-Ox Adventa..