wirecare.com is another one for shielding
WireCare has some harder to find power distribution hardware. Stud strips, Buss Bars, Maxi-fuses, Crosslink Battery cable, and decent looking battery hookup parts.
WhiteProducts.com has Delphi M3382 compliant fusible link wire. They also have Delphi terminal crimpers and an inexpensive "cost Effective" tooling line that make passable crimps if you use em with care.
TheElectricaDepot.com has a lot of Delphi connectors in project quantities. This is a little mom-n-pop outfit run by a hobbyist that got tired of seeing 1,000 piece only minimum orders on the stuff he stocks. They also carry reasonably priced Delphi crimp and extraction tooling along with the tooling you'll find at WhiteProducts under the Cost Effective moniker.
The Wirebarn.com sells project paks of eight or eleven colors of crosslink polyethylene wire (GXL, TXL, SXL). Less than 250ft spools are hard to find. If you're lucky you can sometimes find 100ft spools. The wirebarn sells in 25ft coils rather than 250ft or 500ft or 1000ft spools.
OTOH if you want some 100ft, 250ft, and 500ft spools of GXL, TXL, and SXL wire... DelCity.com, WaytekWire.com, and AWCWire.com are good suppliers.
AWC Wire has wire with tracer stripes and sometimes has surplus leftover partial spools of wire for sale.
Delphi Electronics was a GM subsidiary that made GM connectors, controllers, and harnesses til it was sold off in the bankruptcy during the Obama Depression.