Just add torsion bars...?

Hello, my 1998 K11 seems "glued" on the road in any condition; my other 2002 K11 instead seems to float in a tumultuous summer creek.
I gave a look to the bottoms of both cars and I realize that 2002 K11 hasn't torsion bars. Perfect.
In a junkyard I found a 2000 K11 front and rear torsion bars and the rear axle also (for the brackets).
I would mount these spare on my car but I have a doubt on the front torsion bar mounting: I see 2+2 hex head screws but on my car there are no holes.
In addition to drilling the floor, are there any reinforcements on the inside of the floor?
Many, many thanks in advance for any suggestion.
Hello, some update.
I lifted up the car and the chassis already has threaded holes for the screws: I hadn't seen them because Nissan put protective caps on them.

So I bought torsion bars and rear axle. I ordered new bushes and rear connecting rods. Once all is ready I'll mount all material.

Question: are there differences between my springs (no torsion bars model) and the springs of torsion bars version?
Is it possible that the springs associated to torsion bars are more soft due to the resistence contribution of torsion bars?
I take it you mean antiroll bars?
There is one on the front.
The rear is a panard rod that goes diagonally across the rear axle.
The springs are the same for all models.
Thank you.
Yes, I mean antiroll bars. I took the front one and also the rear one: my other 1998 K11 has also rear antiroll bar (and Panhard rod) and since the old K11 runs as a go kart, I would repeat the schema.
Ok for springs, I'll keep mine.