What type of balancers are these?

Hello there. This is a coil balance system. I'm confident we can help, but first we need to identify exactly what coil balance Series you're working with. To do this we need to see the pivot shoe further down the window jamb that the coil springs connect to. The identity of the pivot shoe tells us the identity of the coil balances. To do this, it's best to remove the entire assembly and show us pictures. We should be able to narrow this down from there. The video below details how to do this. 

That's a huge help, thanks! Your pivot shoe appears to be a match for our 15-177, which is designed to be compatible with the Series 152. As long as your shoe is the same size and design as our 15-177 then the Series 152 coil spring should work well for this application.

That's really up to you. As long as the other parts are in good condition, there's no reason you can't reuse them. However note that if you replace one individual spring, you really should replace them all. You never want to mix old and new springs together; reason being that springs lose their tension over time, so there will be an imbalanced tension.