Big timmy, you may have an aftermarket core in yours?
I know what a snowball is like when working on an old car! Been there a multitude of times.
As for the heater hoses, the box has to be dropped and the hoses disconnected from whatever they connect to under the hood. I found this out when I did my 78 Sedan, and repeated the procedure when having the heater core, in my 73 station wagon, pressure tested.
It was pretty simple when I did my 78, it has no A/C so less stuff under the dash. The 73 was a different story though. I always heard that dealing with stuff under the dash of an A/C equipped car is a pain, now I can speak from experience!
Here are some tips for the heater box removal:
1) Remove the passenger seat, more room makes a WORLD of difference, and less sore of a back!
2) Remove as much as you can on that side of the dash. This includes the under dash bracket and cuby, the heater controls, fresh air vents and ducts, the glove box door, and the ash tray and radio.
3) See if you can get a bounce light, they are great for working under the dash, as they are small, durable, and bright since they use a fluorescent tube instead of a regular light bulb. I use my dad's bounce light every time I work on the car and it helps immensely when working in tight spaces where light is limited!
4) Put some plastic on the floor before removing the box, as there will still be antifreeze in the tubes/heater core. You don't want that stuff all over your carpet. Try to keep the tubes elevated as much as you can to help prevent any spills. It takes some acrobatics with the box but it is doable.
5) Handle the box carefully and don't pry against it, it is very fragile. I snapped a corner off on my 73's box assembly and now the floor vents don't mount properly (they stay put, but are not secured properly).
Hope this helps! The process is still fairly fresh in my mind (I did my 73's box this spring), so feel free to PM me with any questions if they are not answered already.