^^^^^
Its the actual speedometer, not an overlay. It looks like the speedo bolts from the rear and possibly removed from the front? I also don't know about access through the dash?
super easy on a 86. I just pulled mine last night. take off the three screws at the top holding the decrotive cluster cover in place. Then take out the four screws holding the cluster in place. Pull the cluster out gently, unlpug the speedo cable from behind (you have to press the tabs in and squeeze hard to pull out the cable.) tehn unplug all the connectors being careful not to damage any of the printed electrical circuits. Viola! cluster removed. If it's just the speedo unbolt it from the cluster and replace.
I'm sure it is extremely simple to remove but, any ideas of how to remove the trip meter button? Pulling and twisting does not seem to release the button from the speedo.
Finally had some time this weekend to attempt the installation of the 140mph speedo.
The trip meter button comes off with the front portion of the cluster and did not need to be removed for the installation of the speedo. However, if you wanted to change the lense, removing the button would be required.
Everything went well with the installation of the new speedo, but, unfortunately for me, the 140 speedo is grossly inaccurate. While having a friend mirror me on the road at 45mph, the new speedo was registering 10mph. Nothing I attempted helped get the speedo to read accurately.
LateModelResto offered to refund the money or exchange the speedo for a new unit.