https://swclassics.com/engine-harness-v8-w-electric-choke-fits-1981-87-chevy-and-gmc-truck/?gclid=CjwKCAiAq8f-BRBtEiwAGr3DgV5NzTDgZNeDMtGQOfSTyghN6oj5WEwlyt5BOhyd9v2qg83-FmMpRxoC3IUQAvD_BwE

Harness, 200ish IIRC.

I know LMCtruck has pretty much everything for trucks before the 2000s but they're generally pretty pricy, ebay is a good place and maybe a shit-the-bed donor vehicle from craigslist/facebook marketplace?

Chances of finding OEM at that age are slim, but try LMC Truck, JC Whitney, Classic Industries, National Parts Depot.

Those are the usual suspects when I'm searching for parts for both of my early 90s model pickups (a dodge gasser and a dodge diesel)

All else fails, check ebay for used OEM or find a junkyard that has a parts finding network. You'll pay more than normal for junkyard parts but they typically give you a rudimentary quality grading, and can locate exactly what you need (I've done this multiple times too, and the results are usually good)

Would love to help but I don’t have any. Have you tried checking junkyards and eBay listings?