I just dropped in a 350 LM1 engine into my Bird, and ripped out any trace of smog and the old sensors. I've read that the VSS sends signals to the ECM witch in turn sends a signal to the speedo. My question is this: Is there a way to get my speedo to work without the ECM, or do I have to go to a cable speedo?

 

you will have to use a cable unless you find an aftermarket solution. If you still have the ecm...put back in and just connect it to the vss and the gauge cluster so it can run the speedo....thats what i did in my car...the only thing the ecm does is make my speedo work

 

Actually, only '90-'92 F-bods used a VSS buffer internal to the ECM. Your '86 used an external buffer (that little yellow box next the the ECM). It works independantly of the ECM, and will controll your Speedometer, even if the ECM is gone. The ECM is just another "output" to the buffer, so its not needed.