to properly check the condition of a battery it needs to be fully charged
a load tester would be a good thing to bring with you.
other than that look for a date stamp on the battery. I am not talking about the sticker but the date stamp on the plastic case. although this my not help you if you don't have the date code. it has been a long time since i worked for Exide
so I don't remember what their code was. also Exide batteries suck. (my opinion from working for them for several years)
also you should look into the battery and look for warped plates .... most batteries have some warp in them but what you want to avoid is extreme warping. bulging is bad the sides of the case should be straight.
also you can look under the cap and look for a black soot this is usually caused when a battery has been over charged a lot. once again some soot is normal what you are looking for is a lot of black soot. less soot the better.
I hope this helps some.
good luck I hope you find some good ones.
And PS. try to get the same size batteries with matching amp hr. ratings.