the spoilers I used on my car was
69 camaro rear spoiler (this is 2" longer than the 67-68 model but a 1/4" smaller in width)
67-68 front spoiler (this about 1" in width bigger if I remember than the 69)
The spoilers by randy for our cars didn't fit right, he sent me 2 of them, still never got it, I gave up and went for the camaro instead
I also tried a cuda trans am front spoiler but it didn't fit our cars
A cuda rear spoiler I looked at might work but remember they have a flat deck lid as ours has a natural curve to it, and also the cuda/challenger spoiler starts at around $400, whereas you you could get a carbon fiber camaro rear one for the same price
I would love to get my hands on a 70 javalin Mark donohue rear spoiler, I think it would work if you glassed over the rear keyhole, I don't know what the length is for these spoilers
Also to add to this I thought about trying a 69-70 mustang trans am front spoiler someday as they seem to be more flat and looks like they would fit as well...something to think about