I have an 86 mechanical speedo, LG4 computer carb.
Swapped in a 95 T56.
If I get an electronic speedo from a later model, '90 up?, will the VSS from the trans interface with the speedo or does the computer do this?
In other words do I also need the computer from the electronic speedo donor car?
Or
Does the electronic speedo just read from the VSS?
thanks...

For future reference:
Yes the Dakota Digital unit reads directly from the VSS on the trans, ECM is not needed...

 

The electronic VSS would have to be connected to a VSS buffer (small module used on digital dash Berlinettas, digital dash T/As and 5.0 TBI F-bodies) and then fed to the ECM VSS input. The mechanical speedo can't be (easily) driven from the electronics, as far as I know. You may want to get an aftermarket electronic speedo, or a GM electronic speedo movement & install it in your stock cluster & drive it from the VSS buffer module, as well. Cyberdyne may have some insight into the conversion, as well.