Hey man, just wanted to let you know that my gen 2 does the same damn thing. Only mine rattles like a bastard all the time and even the seats have this mouse like squeak to em in hard cornering. But never fear its just part of the charm of an 89 gen 2. That's awesome that you've got an all-trac, I've only seen one of those out here in so cal. Good luck on the 3s-gte swap, its real straight forward and if you need any help on the parts ya need don't hesitate to give el prototypes a call,
www.elprototypes.com. They've done the swap quite a few times and can recite the parts from memory.