Ok.
"Engine Harness" is under the hood. Plugs into the firewall connector (C100), has 4 relays in it, and goes into the interior on the passenger side to the ECM's 3 connectors. All 3 years of engine harnesses are interchangeable, with a minor change in the connector above the brake booster that interfaces with the forward lamp harness for ABS circuits that is easialy changed to what you need.
"Instrument Panel Harness" ("IP") is inside the truck. Begins at the C100 connector, (C100 and the fuse block are snapped to each other) goes across the truck, ends at the 10-pin connector that interfaces to the Engine Harness, and the DRAC connector.
There is a major difference between the IP harnesses for Sy and Ty. Rear lighting and Fuel Pump are in C100 for the Sy and run outside the truck. Ty rear lighting is internal, and has an inline connector on the fuse block. It takes some work to modify one to the other.
There are some minor differences between 1992 and 1993 engine and IP harnesses. Most are associated with differences between the 4-sensor ABS used in 91&92, and the 3-sensor ABS used in 1993. There are a couple of changes in courtesy lighting connectors between 92 and 93.
There are two more harnesses that are not SyTy specific (common to all S-series that have these options). The Forward Lamp Harness is the forward lighting and ABS. Begins at C100, goes up the left side, across the core support. Cross-Body harness goes across the body at the base of the windshield. Goes from door to door for power windows, locks, and in a Ty, the RKE in the center console, and the electric mirrors. This harness is inaccessible unless the dash is pulled, or is rolled aft.
Minor harnesses are: Rear lighting. Fog light. Cruise Control (and rear wiper on Ty). The speaker / radio harness and ashtray and courtesy lights are stand-alone on Syclone. (In Ty they are incorporated into the IP harness.)
I have both Engine and IP harnesses. They have 1993 configuration. Both are brand new, never installed.