Have 2 busted slides....what's the best way to fix/replace them?

I've no idea what year you are working on, but with most of them it's easier to replace the entire slide lever assembly than to try to replace just one or two slide arms. Find a good unit, lube it up with a touch of white lithium grease, make sure your control cables move smoothly and install the slide switch assembly as a whole.

Just want to add this info. If it’s 66 or 67 broken arms are common. Unless you get lucky good units are high dollar. Replacement arms are available Ground Up (http://www.ss396.com) likely has them. 68 on it’s fairly easy to locate good used control heads. Don’t know fore sure about 64 65.