Seen dozens of them. I drove a 68 Dart GT convertible that I bought in South Carolina in 1984 and it had the towing package and it was a 318 with a 727 trans and 8-3/4. You might have seen the car, I sold it to Karl Sturm who owns the Umbrella People that sells the Mopar umbrellas and other toys at all the major Mopar shows. It is now white with a blue interior and a crossram 340. If I remember correctly it had the towing package on the fender tag. I know for sure it had it on the broadcast sheet. I also have a 69 Dart 4-door with a 318 and A/C with a 727 and 8-3/4. It also has ralley suspension with drum brakes all around. I bought it from the original owners son and it seems he wanted a 340 Swinger but needed a 4-door for his family so he ordered it to have all the options of a 340 Swinger but the top engine in a 4-door was the 318. Pretty interesting car and I am still thinking I may restore it and make a good driver out of it one day. It even came with 5.5J wheels and dog dish hubcaps and vinyl flooring!