I'm sure the cardies had more ships than just the Galor that were combat capable prior to 2343. I bet they built the Galors specifically to meet the challenge of taking on Federatoin ships with anticipation to going to war by 2347. After all, Cardassians are known for planning ahead. Besides, 2347 is only 4 years after 2343, so there were probably just a small handful of Galors.