Do you know the baking soda and superglue plastic fix? YouTube search it. If you have the pieces, you can put them all back together, and it will be stronger than the original. And you can whittle it down with a Roto tool if you use too much.
Also, if there are any cracks in your dashboard: I use the Roto tool to take all of the extra vinyl edge off and all of the oxidized foam out, so there was a clean hole, noting rotten or sticking up. Then I filled it in with a hot glue gun. You just have to go slow and make sure it’s sticking to the base. Then, basically, you can overfill it, let it harden, and then you can sand it down flat, and then you can paint it. I did it on my 87, two pretty big, deep, grooves, and it came out like new, literally. I always joke, but I’m dead serious, I painted it with semi gloss black Rustoleum with a nappy roller, so it had a texture, and you couldn’t even see what I did the repairs. A year later, one little tiny, crack has reappeared, not worth fixing yet.
Edit afterthought: even if you don’t have all the pieces, dig in your scrap pile for something that you can carve into the right thing, right shape, and stick it on the same way.