Differant steering rack versions?
But your problem is not the firmness, rather the model application.
Because the LT1 to LS1 motor change, the steering shaft had to be changed to clear the exhaust. If you have a '98+ car and the steering shaft won't fit it's because you were given a 93-97 rack. Or vice-versa.
All I do know is that when we tried to use a 96 rack in a Z28 with a 2000 column, the steering shaft wouldn't work with the stock wheel aligned. There was also a length issue as well.
The ls1 rack angles more toward the driver's side and more toward the back. It has to angle more to clear the alternator and the #1 exhaust tube. The flat is also oriented 90 degrees off and you need an ls1 coupler as well, to keep the steering wheel straight up.
I had this issue when I did the v6 to v8 swap in my 98.
There is a fast ratio v6 rack (which I had as part of the Y87 performance handling package that came on the car) but it still has the v6/lt1 shaft orientation.



