Techically, there is no such thing as "radio delete" on these cars. Radios were an option, it it came with one, it was coded.
If it did not come with one, no code.
Saying "no radio" or "radio not ordered" would be more correct.
Cars with no radio simply had no antenna hole at all. There was no fender / quarter plug.
On the fender thing, I measured T/A fenders, a Hemi fenders, 318 fenders, fenders from 1970 & 1971, fenders from the LA plant and Hamtramck plant and I did find some minute differences. Nothing that would be T/A or Hemi or 15" tire specific, there was no rhyme or reason to it at all.