The R/T never came with 440 signs because the 440 engine was standard equipment. Chrysler had a general policy of putting engine call outs only on optional engines. Thus, R/T's and GTX's got 426 HEMI signs when this optional motor was specified. The 440 Magnum engine was optional on 1967 Charger's only, so had the engine call out. 440 Magnum was standard engine on 1968 Charger R/T, so no engine sign. It has always struck me as strange that Dodge did not market the R/T package on the 1967 Charger whenever the 440 Magnum was ordered. The 440 was not factory available in 1966 Charger or any other 1966 B-body.
I thought the 440 was available in the '66 Charger. The only B body that got one. My memory may be failing me though.