Help no Power to my 78 C20

[ChevyGuyC20]

Hey guys...new here. I am having an issue with my 1978 C20. So last week I used it to jump off my 68 Impala. After jumping the Impala I parked the truck and went inside. When I came out to go to work am hour later the truck would not start. Not only would it not start but it wouldn't do anything at all. I am getting nothing to the starter. No click, whir, nothing. I do have power to my headlights, dome lights, etc...I have been able to clutch start it by rolling it down my hill and popping the clutch. Pulled the battery and checked it on the charger and it is at 100 percent. The brake light on the instrument panel comes on when I turn the key to the on position and then brightens when I attempt to crank the truck, which makes me belive the ignition switch is live and engaging. I am down to what I believe are two culprits, either main fuse link or the starter. Does anyone have any idea of what the issue may be? maybe someone here has dealt with this same issue before? If it is the main fuse link, where would I find it, as I have yet to be able to locate it. Thanks in advance for any and all advice.