Hey Guys, I am a tiny bit stumped here. So I am have just arrived back home from College and I brought my bike home with me. felt like adding some stuff onto it. I wanted to add on a pair of Aero bars and some water bottle holders, when i thought about converting my downtube shifters to Bar end shifters. The groupo on the bike (Takara Elitist) is a Shimano 600, Not Arabesque. I realized that most of the downtube shifters on the market are for 10-speeds or less, as mine is 12-speed. I have never really installed any parts on my bike nor Have I seriously messed with changing or reworking any parts, But i figured now would be a good time as any. However I am having some trouble understanding the research. A bunch of people say that Buying a bar end pod mount is a good option and plop on my downtube shifters, some say that it doesn't matter because what speed the bar end shifters are because the bike is using friction shifting, and I read that the gauge of my gear cable is important too? I'm not sure which is true or if i misread some stuff. So if anyone has suggestion/advice that would be awesome. Also, could anyone direct me to a place where I can grab the parts that I need at an affordable price or am i better off going to a bike shop?

Thanks, Much Appreciated!