Rewiring S-10

I have a 94 S-10 with a 96 4.3 dropped in.I cannot get the ECM to read the 4.3. I was told that the wiring for 1994 is not the same as 1996. (engine,dash, ect) The truck runs but some gauges don't work correctly. Lights, gas gauge, speedometor all work but can't get it tuned right. Also have a 680 Holly carb on it. It reads the 2.2 motor that was first in it. Will I have to rewire the whole motor and dash or is there a way to bypass it. Thanks for any help.

you'll need a new ecm, i think. thats the best way to go, otherwise youll end up doing a slapnut job on the whole thing, and something WILL break.