[Second Series]

That’s some good information from Zoomad75.
I hope your customer keeps the original speedometer. The VSS was in some 1987 trucks. My ’88 has the 5LM60/NP241 with VSS. You have a couple options to keep the original speedometer. The mechanical option is to replace the tailshaft and rear housing. The article I saw was about converting an ’89 Blazer from mechanical to electric, but you could go the other way and get the parts from an ’89 Blazer or something else. The electrical option would be to use a converter box that uses the VSS signal to drive an electric motor to spin the speedometer cable. There are a couple companies that make these. Another option is to modify the original speedometer by putting a stepper motor in it, I’m not a fan of this mod but many people have done this. I decided to make my own and have a motor mounted to the back of the speedometer, not a trivial mod.