According to a 1970 Dodge Challenger brochure, a 340ci engine was not available for an R/T, not even a 383 2bbl engine was available on an R/T. According to the brochure, the standard engine on a 1970 R/T was a 383 4bbl enigine. (See picture). I would think that if the car was ordered that way with a 340, there would have to be a "JS" in the VIN and E55 on the fender tag/build sheet. Just my guess.
True, there are dealer installed options that the dealer installed that may not be noted on a build sheet (i.e. Go wing, etc.) but the likelihood of
a) a roller Challenger (no engine) sent to the dealership so the dealer could install a 340 or
b)the dealer taking out a 383 4bbl engine so they could install a 340. Who would do this?
?
The possibility of either is slim to none, but not impossible. If done, the dealer would note this on the invoice somewhere, I would think. The only way to prove it, and the burden is on the owner of the car, is to have documentation. If it ain't written down somewhere, it wasn't done by Ma Mopar somewhere down the line. Just my 2 cents.
It would be hard to go on just the fact it had R/T emblems. My 1990 Integra had a V6 emblem but Integras were never made with a V6. (I put it there!)
