Sloshing water behind dash?

Maybe before changing out the parts run some coolant system cleaner through for a couple days then change the rad etc and fill with all new coolant. Should get rid of any gunk in the heads/lines/heatercore.

 

I'll do that then to clean out the hoses ect. Gotta take the truck to get realigned anyways.

 

Definitely sounds like the A/C drain line. Look under the truck on the passenger side at the back of the engine compartment. You should see a hose hanging down. Stick a weedeater string up as far as you can and see if water comes out. You can also blow compressed air into it gently.

https://www.youtube.com/watch?v=wZ6oupFWKoM