I won’t need to buy them separately. Heck, in the early days I bought so many envelopes of KD#5’s where never needed the draft gear box, that I’m sure I have a bunch of them around here somewhere. I never threw them away. Any time I have used them I used screws to hold them on - either in the center spot or the two side holes - last time I mounted a set was a few months ago on a brass caboose - thats how they are done.
One of the first pics I took with my digital camera of the layout back in 2011 was one of my Chessie System SD40-2 locomotives in my Columbus (OH) staging yard. Last month, I finished converting all of my rolling stock to Kadee couplers, which look much better. 
My first Athearn locomotive was my Amtrak SDP40F (actually an FP45), which still runs.
http://www.youtube.com/watch?v=YnHPPiKY7Kc
Three of the four trains in this video were pulled by blue-box Athearn locomotives.
http://www.youtube.com/watch?v=hoTU5Bp4kyw
Kevin
,
I have I very similar story including joining the Navy however my old trains rotted in a box from 1986 to 2013 when I took them out to show to my youngest. The only ones that worked (and not great) were the BB. I cleaned them up and was hooked again. since I have been having a great time rebuilding and kit bashing. I still remember buying my first BB Athearn and how well it was made compared to most of the stuff available at the time. For those who would rather dump their old BB in favor for something done and ready that’s great but HO was the choice for Modelers and it was the scale for those who wanted to make it their own. Toy collecting was always the O scale guys. I have bought a few of the Athearn Genesis w/ sound and there nice however they have nothing on one that I have cut sanded upgraded and rewired.