Older MacBook Pro (Early 2008) 15 in, battery question

I own an older MacBook Pro (Early 2008), 15 in that we have replaced the power cord and battery pack a couple of times on. They are both due to be replaced, the battery back because it's not maintaining a charge longer than an hour, and the power cord because our Roomba decided to eat it yesterday! I've been doing a bit of research because the Apple Store employee said they no longer carry "vintage" batter packs and if I'm understanding everything correctly, it's lead to more questions. It seems that the last person to sell us a power cord, never pointed out that there was a difference between the 85W and 60W. Our machine is supposed to use the 85W but we were using the 60W. I can't find where that was a problem, but it might explain why its taken longer to charge the computer and never charged "as well", per our daughter's observation. Here is the new question that I'm having problems researching an answer for….what battery pack should I be looking for that is specific to this machine. I am currently using a model A1175 10.8V 60W, but the 60W is making me think there is supposed to be a different one out there for the computers that use the 85W adapter. I researched the power adapter on the Apple website and it states that the original equipment for this computer was the 85W Magsafe T style. Unfortunately, I couldn't find a different location to research the original battery pack model numbers. Thank you.