Help on replacing the heater core with A/C??

[Bigo Serge]

What up fellas,
I'm new here. I got a 72 cheyenne with A/C, and want to know if anyone can guide me in the easiest way to replace my leaking heater core. This isn't my first rodeo with heater cores. I just haven't had to change it on this truck, and I thought I could figure it out as I go on.
So far I have....
1. removed my glove box
2. removed the center air ducks form under the dash with the bolts.
3. removed the bolts that holds the heater core, it just won't budge.
what clips or bolts am I missing?
I have read that the inner fender has to be dropped on the non a/c trucks, is it the same for the a/c trucks? Any pictures will be greatly appreciated. Thanks for everyones information.