Metra also has brackets(plastic) - #02-4544 & - #02-3320.
So does Jensen. You might even try using the brackets
from the mid 80's radios. Just drill different holes. Probably
pretty cheap. I'm using a set of these for the test fit on my
85 SS. I also found the mounting brackets for the dash on 86 -
88's on Ebay for $20. They're from a 87 Caballero(El Camino).
Larry.