If the rear drive shaft feels to tight or out of balance, it's possible it just needs to be lubed at the grease fittings.
Try looking through any receipts that may have come with the rig for more specific info, because sunroofs weren't offered stock in the VX, so it's most likely an aftermarket purchase...or from the sound of it...also quite possibly a Dodge sunroof out of some model vehicle from that brand since that's where all the other donor parts came from. I think your best bet for info on that one is going to be to talk to the previous owner again.