The Painless etc harnesses are anything but. You'll get just as familiar with crimping Packard 56, Pak Con, and Weatherpak terminals on one of these harnesses as you would just plain repairing yours.
The PVC (Poly Vinyl Chloride) jacket General Purpose wire sold at most auto parts stores is just plain garbage. PVC gets brittle at temps below 30°F and progressively more brittle as the temperatures drop below that. I use Crosslink Polyethylene (SXL, TXL, GXL) wire for all my repairs. The GM wiring diagrams specifically state SXL and GXL in several places. SXL is the heaviest thickness jacket so I typically just default to that. You can get small assortments in 25' coils on evilbay. The larger outfits that sell to the public like Waytek and Del City sell in 250' and 500' spool minimums.
As far as wire colors goes... Crosslink poly wire in many primary colors with various color tracer stripes is available on evilbay along with the more common solid color wires in several gauges.
A Brady BMP21 label printer is quite tough and it can be purchased at Home Depot. It runs for quite a while on 6 AA cells. It'll print wraparound adhesive labels for the ends of individual wires or the split poly or mesh sleeve just behind connectors. I use the nylon cloth label cartridges.
Tools to crimp a wide range of connectors aren't terribly expensive. Here's part of my post from my 2005 2500HD build thread.
--------------------
If you do any automotive or motorsports electrical work you do not have to buy the crimp tools that crimp the pins for one connector family only in one operation. That type of tool is real nice but it's expensive and not versatile.
Delphi made two very versatile ratcheting terminal crimp tools that are inexpensive for pro level tools.
They crimp terminals in two operations. The conductor is crimped in the proper cavity for that terminal & wire gauge. Then you move the partially complete assembly to another cavity where the insulation or seal wings are crimped in a second operation.
I've crimped Deutsch DTM & DT open wing terminals, Molex GT, Metripak GT, Metripak 150 & 280, AMP Quadlok (VW AUDI), Weatherpak, Packard 56, and several other families on 14-20ga wires using the two Delphi tools. $220 for the pro level tools is a bargain for that versatility.
They cost between $90 & $130 each but you can position the terminal and ratchet the tool down and re-position the wire without loosing the jaw closure. They will not open til you have completed the crimp cycle or cammed the emergency release open so you don't end up with an over or under crimped terminal. You can likely evilbay these off for $95-$100 each if you take care of them and suddenly decide you don't need em.
-Delphi Ratcheting 12085270 Crimps Weatherpak and Metripak 150/280 sealed terminals... Three seal and two conductor wing cavities.
-Delphi Ratcheting 12085271 Wide range crimper with five cavities for conductor and un-sealed insulation strain relief crimp wings.
If you need to crimp Metripak 480 or 630 or Packard 59 terminals you need larger cavity tools but the above tools will crimp 85-95% of what you're likely to encounter.
These are some less expensive $30ish non ratcheting tools. These are great for the weekend warrior that's crimping a few terminals or as a tool to hold you over til you can find a nicer one. You'll tire of them quickly if you're building vehicle harnesses for your hot rod or restorations. One downside is you can open them before the crimp operation is completed and end up with loose crimps and they don't have the positive stops of the more expensive tools so you can over crimp the terminals as well. They also tend to wear faster than the pro level tools.
-Wire and weather seal crimp tool for Weatherpak and Metripak 150/280 sealed terminals.
https://www.amazon.com/dp/B002CCAEJ6
-Wide range wire and jacket wing crimp tool for unsealed and sealed connector conductor wings. This tool will not crimp the Weatherpak/Metripak/Molex-GT weather seals but it will crimp the conductor wings of those families and both wings of un-sealed terminals.
https://www.amazon.com/Delphi-Packar.../dp/B003MWJ6SA
------------------
DO NOT throw out the plastic connector shells. Many of them are obsolete or very difficult to find. The terminals inside are usually fairly easy to find.
You need to identify what terminal family you're dealing with. The GM wiring diagrams have the connector shell part numbers in the diagrams.
A very helpful individual has already put together a long writeup about re-using connector shells here.
http://www.rowand.net/Shop/Tech/Reus...iringPlugs.htm
This is his terminal identification page.
http://www.rowand.net/Shop/Tech/Auto...Connectors.htm
GM Service Training Group put together a color booklet on terminal extraction and crimping. I scanned it and posted it in the 73-91 manuals.
GM_STG_18001_02_VA_Wiring_Assembly_Repairs