Removed and replaced the old water pump. Definitely was leaking thru that weep hole.
I didn't see on my maintenance log where the belt and tensioner have been replaced (but I did replace the AC belt and tensioner previously), so I'll order new ones later. Tomorrow I'll stop by and buy some Dexcool to replace.
It took me about 45 minutes to do the job. I didn't know this, but i had installed sealant on the water pump bolts on this truck when I swapped the engine. You don't have to do that because, unlike the previous generation engines, on the LS the water pump bolts are blind holes. All you need is the gaskets (no sealant on those either as I was doing before.)
I spent about 10 minutes cleaning the old thermostat sealant on the water pump bolts. SMH