Ok so I need to replace my heater core. I think I know how, so that is not my question. What else should I look at doing while I am in there replacing my core?

 

Speakers, the foam / rubber / whatever spooge it is around the heat control door, any sound deadening or sealing anything you touch

 

new heater hoses

 

I've noticed little pads on some Thirdgens where the dash pad and dash touches the body. I was thinking it is there to reduce noise/squeaking etc.

Could clean out the HVAC ducting as well.

 

I was thinking about doing a little sound deading when I replace the carpet. I would like to do a spray on type while everything is out for carpet.

 

I would suggest an alluminum heater core replacement and careful not to bend the tubes too much on the brass ones, or they WILL leak.
Not sure if you will have the "hidden bolt" on top of your heater box, but I would guess yes. It's a feel for it type of thing. And carefull putting new one in, goes in at an angle to some degree.