Without the R/T for Plymouth, what determined the 426/440 assignment?

[bull]

I've wondered about this off and on but it never concerned me enough to ask... until today I guess. Since the Charger is a Dodge we always go round and round with people who say their XP or XH Charger came with a 440 because we know Chrysler didn't do that. So what determined this on the Plymouths? There are no R/T Plymouths obviously so did it have to be the 'cuda rather than the Barracuda or the GTX instead of the Roadrunner? Or was it primarily a VIN thing?

[el dub]

I think it was an option thing.  The GTX was the top of the line Plymouthy B body. Just a guess.

[68X426]

Speaking for 1968, VIN is the assignment. The Road Runner had the 383 as standard (H in the VIN) and Hemi as the only option (J code) and no 440 offered.

The GTX had the 440 as standard and the Hemi as option, no 383 available.

I think it's reasonable to say that the GTX was the RT equivalent for the Plymouth line.

Satellite and Belvedere could get you any motor, Slant 6, 318, 383 H or G code, 440, and 426. I believe that a Sport Satellite could be ordered with more equipment than a GTX if the customer really wanted every option.

[68X426]

Oh yeah, it's an "L" code in the VIN for a GTX with 440, 1968.

The engine letter is the "assignment".