ok here is what we did. first off i have a 1991 Firebird (the 86 in the name died on me) it had the stock 3.1L V-6 in it. it spun a bearing. I got a 305 motor for free out of a 86 Monte carlo. Had to get a new Trans so i picked up a 700R-4 Trans from this guy that was selling it for $225 so i picked it up. put in a transGo shift kit and swaped out the rear cone out it. Now the new motor has a carb so i get a HEI Dis. we took out the wiring harness to the ECM and took out all the wires and relays that we needed for the Tech, Water,oil and so on. But the speedo was ran in the ECM so we already know it will not work. so i need some help here. is there anyway that we can keep the STOCK speedo ???

 

I think 91,92 third gens speedo are electronic.Since your computer is dead,Im guessing you would have to swap in an earlier instrument cluster and speedo cable.

 

http://www.hioutput.com/tech/speedo.html

 

where is that little yellow box on my car? or do i have to get one or what?

 

i believe that the speedo has to run on the ecm in the 91's. also i believe that you have to get a speedo from an 8cyl car as well.
because the 6cyl speedo isnt configured for the v8's.

-earl-

 

The speedo in the 91 is the same that is in the V-8. as for the EMC thing i don't know. after reading that link in the other post it sounds like it should work. just have to find that *** damn box. but i looked ALL day today trying to find it and no luck. i reran all the wires today for it just have to find the box.