Dylan, I just read through the entire thread. I am very glad you're enjoying your pickup, and working on it. Mine was the first vehicle I ever purchased, so I've continued to work on it and update/upgrade things on it little by little over the years as desired/needed. Despite my friends not understanding why I keep and work on a 25 year old pickup when I own two other newer model vehicles, I simply still love my chevy. This was one of the best looking body styles GM ever put on their trucks. There's just something special about this 1988-1998 series, ya know?
I enjoyed reading each post and what you've been doing along the way. On more than a few of them, I smiled while thinking to myself, "Yeah, I know all about that one, been there done that with mine too."
You're still working on many of the higher priority things right now (obviously), but when you get to cosmetics and other replacement parts, I'd be happy to share links with where I found certain parts for good prices if you need it. Also, there is one thing that almost universally goes bad on these trucks (1991 models), or at the very least, the handful of people I know that have this same model year inevitably ran into it sooner or later the same as I did. That one thing is the windshield wipers will up and sporadically work or not work one day. Then, within a month from that happening, they'll just stop working altogether.
It will be the wiper motor failing. Just save yourself the hassle of trying fuses, checking wires, and everything else the rest of us tried when it happens. You'll have to source a refurbished one somewhere, as I don't think there are any new ones left anywhere that I could find. Took me close to a year to figure this out after searching, and I became very versed in driving in rain with no wipers. (I got so used to it, that I sometimes now forget to turn the wipers on when it rains in my newer vehicles, and if someone is riding with me, they start to freak out after a while, hah hah.)
But yeah, if it's a 1991 Chevy Truck, the wiper motor isn't a matter of "if" but "when" it will happen to you. Unless the previous owner already replaced it in the past eight years sometime, you will need to at some point. They aren't terribly expensive, so keep your eyes open for one and go ahead and set it aside.
Hopefully I'm wrong, but maybe it will happen, and you'll have the replacement ready to go sitting on a shelf in the garage, and you smile thinking to yourself, "Ah, that one guy online actually was right about this thing."
Anyway, love what you're doing with your truck, when I look at it, I see many things (rusted fenders, cracked grille, etc) that mine had when I bought it. When I see yours, I see past those things to the goal you're working towards and the potential there for a great ride. (You already replaced the grille, I only just finally replaced mine last year!) I'll continue to check this thread out from time to time, I'm getting some good ideas from you too on some things that I haven't done to mine yet.