@Leon Cream, You may already have this information, if so my apologies. The chassis that you’re using for a donor is Laughlin style “front steer” chassis. Monogram used them on the GM kits, but they are interchangeable into a Monogram Ford body. The kits with the Laughlin chassis’s didn’t have front springs for some reason.
The Ford Thunderbird kits came with a Banjo Matthews style “rear steer” chassis. They did come with front springs. These will are also interchangeable into the GM bodies.
Maybe @Dave Van can chime in with more information. He’s way more knowledgeable about these kits than I am.
Edit, After looking at your pictures again, those lower control arms look like they came from a later Monogram kit, maybe from a Lumina? If so, that most likely blows my earlier comments out of the water. Sorry for any confusion.