Welcome from the Motor City ! I See it was a ZY5 optioned (Exterior Decor Package) Light Blue Metalic and Silver, Would be cool to restore it that way !
These Pass-Port Sliders are the closest to Factory Sliders.
They’re good quality and use the same window seal as solid glass rear windows.
There is one available on ebay…
Shop around for sure, most Vendors get their parts from the same Supplier/suppliers.
I’ve had good luck with CJ Pony Parts, Truck Shop, JEGS, Classic Parts.
Order Early ! turn around time sucks now.. Sometimes many months
That appears to be a good quality Part, Hopefully you’ll have a good fit around the gauge Bezel. As mentioned previously, it’s a common problem, here’s a pic of an original factory dash pad vs a poorly fitting aftermarket one.
it’s been a couple of years, thought I’d repost this very informative article
Body Side Moldingshttps://www.streettrucksmag.com/77-c10-installing-mar-ks-body-side-molding/
Welcome from the Motor City, Great looking GMC !
It deserves a GMC Grille. The ‘75-‘76 GMC grille is one of the most sought after. I see them for sale on eBay, usually $150-$400
I restore and sell original show quality Bed Rails, I have 3 sets of Short Bed and 2 Sets of Long Bed ready to go. All new chrome, Woodgrain, polished aluminum and New Stainless Hardware. PM me