Yup, almost all MJs had the vac disco. To my knowledge, only the 86 models with the all-wheel-drive option had the non-disco.
Apparently the vac disco survived into '93 on Cherokees. '93 is the last year in car-part.com that give the choice of vac and non-vac. '94 the choice disappears and I assume the vac disco was gone for good. But, if you search the nation's junkyards for a vac axle, the vast majority of the results that turn up are '90 and '91. '92-93 become increasingly rare so I imagine that Jeep was in the process of dropping it.