That could be true-the distance between both cases is very far, but the person(s) who did this could have always traveled.
When crimes like this happen, I always try to look to see other cases. It's difficult sometimes to look into murder cases because there usually is not as much information from cold cases like that, unless it's the Black Dahlia murder.
This is a great possibility too though, if that was the case, the person(s) responsible may have been targeting young girls in groups, which is a little bit unusual. What would the motive be for taking these girls?
Going on that theory, on July 31st, 1974, Cynthia and Jackie Leslie also vanished on their way to a party in Arizona. The party was supposed to be just a walk down the road, it is unknown if they ever even made it to the party.
In 1983 Louisville, KY, 12 year old Ann Gotlib vanished and her last known whereabouts was at the Bashford Manor Mall, where she rode her bike to, which was later found dumped. The suspect was Gregory Lewis Oakley Jr, and authorities say if he was still alive now, he would have been charged with her murder and abduction. From his pic I have seen at this website, he somewhat resembles the suspect composite for the man who took the Lyon Sisters:
http://www.charleyproject.org/cases/g/gotlib_ann.html
A lot of people may discredit the Lyons sisters being connected to the Forth Worth Trio, but I also remember that authorities think the Lyon Sister abduction is connected to the '76 abduction of Dorothy Scofield-and FL and Maryland aren't the closest together either! (or it could be there are multiple diff. perps who committed these multiple crimes).
But if they are indeed all connected, could it be possible these ppl were involved in a human trafficking business with selling ppl into slavery rings?