One of the reasons on line decoders are so unuseful is they fail to distinguish WHEN certain codes meant certain things. Codes changed from year to year.

According to the white books, J42 did mean pistol grip shifter in 70-71.

By '74 J42 probably means some sort of accessory or dress up item on the car. It could be tied to an A code package. I don't have the information readily available as to what J42 could be tied to but I will look later.

The code can be found on US tags, so it is not unique to Export (I code) cars.

We also have to consider that Windsor plant (R code) does use some codes not normally found on US sold cars decode information.