You would need to fully disassemble the 87-89 cluster, remove the actual speedometer mechanism off it's plastic frame (which the gauge face is glued to) and swap it over to the plastic frame that the 90-93 speedo is mounted to. Then you would need a 90-93 style 140MPH gage face unless you can carefully transfer the 87-89 gauge face over.
I'd ebay that '88 speedo, as it will drop in fit the 87- 89 cars, and buy a 90-93 V8 speedo. You should make money on that deal since the speedo you have is rare compared to the later model one. I sold a 140 MPH Motorsports speedo for about $100 a few years ago.
I'd ebay that '88 speedo, as it will drop in fit the 87- 89 cars, and buy a 90-93 V8 speedo. You should make money on that deal since the speedo you have is rare compared to the later model one. I sold a 140 MPH Motorsports speedo for about $100 a few years ago.