I don't think they are as close aligned as you might think.
Plymouth appears to have been better at following the fresh air for all Hemi guideline than Dodge was. hemicudas got mandatory shaker hoods, Hemi Challengers did not. 'cudas could have red bubbles on red cars, Challengers could not (I understand that the promo car(s) may have had orange bubbles)
The shaker started out on Challenger as Hemi or Sixpack thing only, then added 383 and 440 4 barrel. However since it was an R/T only thing in 1970 it appears it was not available to the A66 Challenger 340. Where as you could get a 70 cuda 340 shaker.
As stated above, very true. And like I said, S series models (JS/BS) only for 70. The A66 Challenger was a JH so again, being in alignment, no shaker for the A66. However, for 71 we see the JH now available along with the JS/BS. But nothing for the BH.
