With wiring schematics or analyzing the switch of the Newport system it should be possible to use a original switch with some modifications. The wiper wiring is not rocket science. Maybe that's worth a try.
I have the experience that these cheap fuel pressure regulators tend to fail in a short period of time. I never saw one older than 2 years still working. Friend of mine bought one and it was broken out of the box. Just my 0.02$
Mpg on a brick shaped truck is never going to be great. The rwd conversion is fun to drive and for donuts. You could swap a np205 or np208, both have rwd.
Swapped a 454 into a friends K5 a few years ago. We did it in 8 hours with no rush. We were prepared, had all needed tools, hoist and fluids and we both installed/swapped engines before. Without experience or friends who know what they are doing not so easy.
Welcome from Austria.
The DRW was optional and the SRW was stock.
This is a link to a .pdf from GM heritage site. It's the brochure for the 1982 trucks. All options are listed there...
Techflex split wire loom. Pricey but great. Lots of other stuff like heat protection too.
https://www.techflex.com/general-purpose/f6-woven-wrap?product_selected=F6W0.13BK
https://www.techflex.com/general-purpose/flexo-f6
Depends one the use. If you need your 4wd only sometimes in winter or on dirt roads you could leave it as it is.
If you drive offroad a lot lengthen it. my 0.02$