I would think so, they were 2 separate options. In '72 you could.
Starting in '73 to '74 there were no more separate Rallye models with the "JS" designation in the VIN, all the Challengers in '73 and '74 were "JH" cars and the Rallye became an option package, I believe code A57.
Conversely, I believe you could order the Rallye option package with a 318 car. Even in '72 you could have a 318 Rallye car.
Soooo....in '73 I think you could order a 340 Challenger and not have the Rallye option, but someone else might want to add to this.