A 1998 29er? I think not. There is a Giant Farrago hybrid from around then, but that's a hardtail.
But maybe you're referring to the suspension seatpost?
And the one I can find is listed as having an 1 1/8" headset.
Remember that a 1 1/8" threaded fork will take an 1" quill stem.

Well...
On the forks that I've seen any specifics, they've used a method called "cryo-fit" to install the steerer tubes - basically keeping the fork crown at room temperature and cooling the steerer tube to some serious low degrees before inserting it. I wouldn't feel comfortable in pressing one of those puppies out, and I'd feel even less comfortable in mounting a new steerer with a bushing.

With that said, I have mounted an 1" steerer to an 1 1/8" stem once. With steel, the steerers are pretty close to a good fit to start with.
I cut the 1 1/8" off flush with the crown.
Some slight reaming and a bit of heat and they went together smooth as butter.
Used some silver solder with good wicking action to lock the pieces together.

Just to be clear: Being able to do something isn't the same as being able to recommend it. If you go this route, you're on your own.