i used this info from a moparts thread of many years ago-it works.
all the best
frank.

Here are some measurements I took from mine BEFORE I restored it. The car had all original paint, so I'm sure the emblems were original as well. Letter T of the R/T: 2.5" from the pass side edge of the trunk lid, 0.75" from the rear edge of the trunklid (without the molding). The letter R of the R/T: 1.5" from the rear edge of the trunklid. The Challenger emblem is 1.5" from the rear edge of the trunklid (again, without the molding), I took the measurements under the letter "h" and under the letter "r". The distance between the letter "r" or the Challenger emblem and the letter "R" of the R/T emblem is 0.75"