Hey Bart,
There are 8-10 Nuts you need to remove from the underside of the dash, they are 10mm nuts. You will need to remove the instrument cluster-(I work on 72-73's so if there are differences, someone correct me.) There are 2 screws in the instrument cluster on the top, remove these and tilt out. I use a long screwdriver to compress each side of the instrument cluster multi connector. Then remove the speedometer cable, squeeze (compress together) while pulling... Later models have a few other small connectors but overall that's it. You then will be able to access all the nuts under the dash. 2 nuts hold the dash speaker mount so remember to put this back in when you put it back together.
Hope this helps.