I have a 4.3 Vortec CPI engine from a 1992 Jimmy that I am installing in a 1981 Mercedes 380 SL. Have preserved the entire wire harness that relates to sensors to ECM, eliminated all other wire. Is any of the other wiring, dash etc necessary for the engine to run well. Anyone have any experience with this type of swap?

 

As long as all the "inputs" & "outputs" to the ECM are wired up correctly - no, nothing apart from that should be needed on a 92.
It's pretty much the same as the 94 and has separate ECU's (boxes) for everything. (A big advantage).

I ignore if it requires some inputs from i.e. the brake switch, VSS and such. A/C may have an input to the ECM. Evaporative has some stuff as well (canister purge/EGR). But nothing related to the dash AFAIK. Then there is the questions about the ignition switching, relais for the ECU/engine. Are you running with a manual or automatic transmission?

The OEM service manual including the electrical & diagnostic manual should be available for some 20 - 30$ on CD-ROM. Have a look at rockauto.com. This will show all the required inputs and also help in troubleshooting.