What have I done? Video attached: Bad sound after oil change on ol' Blue

[PanhandleShantyman]

Anybody recognize this sound from the linked video below? It's definitely metal hitting metal and I'm worried I'm headed for damage if I don't find it soon.

Today I gave the 1969 GMC 1500 (inline 6 250, 3 on the tree, no modifications) an oil change. I went to drive it after and once it had warmed up, I started hearing this loud, irregular TINK TINK noise from the front of the truck. The noise became more frequent as I continued to drive it back home. It is also more frequent with the truck in gear and getting gas.

Only other thing that happened to the car today was that I had taken it down the hill and turned it around and gunned it up the hill in reverse to get it in position for the oil change in my driveway. It's kind of a steep hill and to keep it from rolling down on my I admittedly clutched it at high RPM and it did "kangaroo" on me pretty hard on the way up. Enough that I gritted my teeth and thought, "oh that wasn't good for it." But I didn't notice anything wrong at the time as I pulled it in the drive for the oil change. I put in 5 qts 10-W-30 and a new oil filter.

Anyway, later, trying to figure out where the noise was coming from, I initially thought oh no, I must have messed up something in clutch or drive train with that hard gun uphill in reverse, but the sound is not coming from there. It's coming from the front end, from the fan area or maybe up to a foot behind it. I can't isolate it with the stethoscope, listening to the engine block, alternator, or radiator. Putting my hand on those areas, I also don't feel a vibration when the clang happens. The fan doesn't seem to be intermittently hitting anything. It's a TING/TINK/CLANG kind of sound. I put a link to video below.

I'm not sure how the hard reverse or the oil change itself would start this noise happening, but it's definitely from something that happened today. It's been driving fine to work and back for the last month since I got it running reliably and fixed all the electric stuff to get her street legal after buying it from the previous owner. I haven't done anything particularly invasive to the truck, just rebuilt carburetor, replaced I/O manifold gasket, steering wheel, and a lot of work on stuff like taillights , horn and heater. I did put some radiator stop leak in it a few days ago too.

Any ideas where I should look next for the cause of this? Worst case scenarios to check out first to prevent damage? I'd appreciate y'all's thoughts, I'm afraid to drive it like this and I want to find the issue fast without letting any additional damage happen from whatever is banging around in there.

Thanks!
-Will

Video link below:

https://youtu.be/K9P0g_WFMww