I'm sorry I'm not familiar with legendary Auto interior dash pads but I will tell you that some of the brands out there are made with ABS cores. As far as I know just dashes and ABC moparts are the two that refurbish dash pads and have a steel core. A steel core is preferable to avoid any potential warpage from extreme heat . Some have reported that ABS cores can have some vibration while driving.
Unfortunately I don't have any experience with changing a dash pad in place but from my understanding it can be done but the front four screws require some creative use of I'm extensions and swivels. I decided to refurbish my entire dash so I pulled it. I was surprised how easy it was. When the steering column down it was a matter of literally four screws in the front the two nuts on the side and disconnecting the fuse box heater cable wires in a couple of vacuum hoses. Once you have the dash out it's nice because you can go through and fix wires and light bulbs etc. I've included a couple of pictures of my dash frame mounted to the jig.
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