Frankenduster summerized the opinion on the situation.

There's a few things to look at in terms of construction; geometry, attachment and integrity.
Since the K's are not all the same, their rigidity is not all the same. When there are problems, they seem to primarily be the steering box mount, and integrity. By the latter I'm refering to seams that were a bit open when welded and things like that.

Since you (the OP) are going to be using this only as a driver, there is little gain to be had here if the integrity is OK. With sticky tires, high rate springs, sway bars etc, then stiffening the chassis becomes important. That said, poor weld joints and highly leveraged steering boxes can be a problem even on street driven vehicles. For example, there were some Dodge vans that had a reputation for having a problem with the steering box mountings.

My only caution to those with much stiffer springs etc is that if the car will ever be used for competition, be aware of the rules. Some sanctioning bodies do not allow seam welding in certain classes. In these cases care should be taken that the welds look to be either factory or acceptable repairs.