69 Dart GT emblems and decals

As far as the jack instruction decal is concerned the procedure on the assembly line goes something like this.... line worker stood on the driver's side of the vehicle, with the decal in their right hand he or she ( political correctness) would just slap the decal on the underside of the trunk lid as the vehicle continued pass. With different workers of different arm lengths and heights weights etc there is no real perfect location. Remember it's just a sticker on the underside of a trunk lid. The line worker is probably installing one every few seconds or minutes along with other operations. Sorry to be the bearer of bad news but a dart in 1969 was just a car and a low level vehicle despite what there worth today. So just peel off the decal from the paper backing and slap it on. Wherever it lands is correct.
Good luck with your project.