I have posted this question on the Buick Club site.
One person with a 60 series said he had removed a dash and it was bolted plus a sticky adhesive. He said the bolts are visable when he opened the door.
No one else has been able to confirm whether the 80 series is the same.
My dash looks like it is welded on to me, but I've been wrong before so I thought I'd ask on this site.
Thanks