Once your steering starts to make noise and becomes difficult to turn the wheel (it's called "morning sickness") the only real way fo fix the problem is to R&R the rack. You might consider a new pump and hoses too. If they are OEM, those pieces are 15 years old.
Once concern I have always had when I think aobut the possibility of having to do this on my 87 is whether or not the parts stores can tell the difference in a Z51 or base rack by looking at it especially if it's a remanufactured part. Either rack will bolt in but how can you really tell if you got the correct rack until you turn the wheel??
I would definately replace the Z52 rack with another one as once a new rack is in place and a good alignment done, the steering effort will be much easier and the quicker ratio is worth any additional price. If a Z51 rack is the same price or close, I would go for that one. Steering effort should not be really noticable between them. The big difference will be between the bad one and a new one.
BTW, GM offers a "cold weather" PS fluid and you might consider using that fluid year-round.