The E-Series 1983 and older used "Coined" wheels. Alternating recesses and protrusions served to lock he rear wheels together. An index pin forced the wheels to go be installed only the correct locking way. The the lug nuts finshed the centering AND carried the load. Later E-Series have the Hub-Centered wheels and the Swivel Nuts only hold the wheels against each other and the hub.
I wanted to replace our 16.5's on the '83 we had adn realized there was an issue. Then one day blew a tire on a trip and simply replaced all the tires plus the spare with new 16.5's. That was 13 years ago. If I had it to do today, I'd look for a set of 7 16" Coined Wheels.