Ducktail spoiler for 74 duster

that’s what I was think of doing to!
Well then, you will need to rethink how to mount it or the cracks will show.

It needs to be fully glassed in rigidly so that wind and body flex doesn’t cause cracking of the joints. This means glass mat and an understanding of Custom of body work.

Research and learn and don’t try to learn the hard way...and you can do it.