You are going to have to do some welding , drilling and parts replacement
on this diagram
https://www.partstree.com/parts/husqvarna/mowers-lawn-garden-tractor/yth-18542-96013000202-husqvarna-yard-tractor-2008-02/mower-lift/ replace item 11 + 12 + 19 x 2 + 2.
On some mowers item 2 can not be removed so you either need to build up the flogged out holes or position 11 & 12 in different holes.
Note there are two bushes , item 6 these will also be shot & need replacing.
Then at the front have a close look at the two drag links , item 15 if they have deep grooves worn in them either replace or build them up the same with the pins , item 17.
Then look at the holes where the pins and drag links run in.
They will be flogged out oval as well.
So weld up the holes in the deck & redrill them or move the link to a lower hole.
On the mower end, pins ( Item 17 ) fit into a hanger.
On some mowers it is a bolt on replacement while others it is welded on so it is a build up & redrill job.
As you can see this is a lot of work.
Charged out at a shops regular labour rate you are talking 2/3 the price of a new mower.
I have done it, or part there of on a few occasions, we got one up to 4.5" cut height.
Any more & the belts rub everywhere and you end up fouling on the drive belt as well.
