Here's a simpler answer to your 3 questions:
>>> 
>> 
>> So, were front and rear wheels different on these older vans?  

NO

>> Does that mean that tire rotation required removing the tires from the wheels and remounting them?

NO

>>  Did one have to carry two spares in order to have a wheel to mount front if needed, and one to mount rear if needed?

NO

>>  All seems needlessly complicated and a real functional problem.

Huh?

>