The old model a wheels centered themselves on the hub. The bolts don't take any weight. Supposedly you can use these wheels on later juice brake hubs if you get the spacer/adapter. The reason is not because of centering, its because the juice brake hubs do not fit flush up against the back of model a wheels. There is a small space in the center, so when you crank down the lug nuts, you can crack the center part of the wheel.
I think just about everyone will say that using model A wheels is not a great idea from a safety perspective. Although Model As weighed almost 3000lbs and had brakes good enough to lock all 4 wheels at highway speed...so I don't know. Im sure they won't take much cornering force though.