There are 2 fuses that control the clock. One fer operation and the other fer display. I'm gonna guess the CIG and DOME fuses...one of those are blown.
If yer putting POR-15 on one spot...you'd better give the entire truck a good look over...especially on top of the gas tank where the fuel pump lines come out. It's notorious fer rusting/leaking there...
I think I'd go with a high temp paint after you put some of that rust converter paint on it first.

But clean up that pan really well with some solvent...and wear yer safety glasses/goggles!