hi there,
I have actually just started the process of doing the heater core in my 78, it does not hav AC, and really doesn't seem too bad to do. I am not currently driving the vehicle, so i can take my time, (i slack hahaha)
but i do live in BC, canada so when the fall starts i will need it. BAsically, i was having a whole mess of trouble, untill i removed the glove box, then everything becomes pretty open and easy to see.
As long as you have some mechanical ability, (and it doesn't hav A/C) i dont see you having much trouble.
Good luck.

