ignition harness?

Other fords of the same vintage use the same switch. You might just get by with only replacing the connector shell.

Some vendors other than the obivious junkyard source..

http://www.50resto.com/
https://fordparts.com/acc/
http://www.mustang-unl.com/lmparts.htm

Wiring parts and connectors
http://fordfuelinjection.com/products.html

online Mustang junkyards
http://www.stangparts.com/

Diagram courtesy of Tmoss & Stang&2birds
View attachment 357761

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel pump, alternator, ignition & A/C wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Computer, actuator & sensor wiring
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Fuse panel layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

Vacuum routing
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg