Today I have purchased a ka linkage to make investigation with it. It`s the same shape but not as quick as puma ones. I think the bars are about 1.5 - 2cm longer in the puma linkage. But this is easy fixable by shortening and welding the bars I think. Also you can mount the linkage directly with the original length bars and maybe trimming a bit the floor it has no problem. Also the lever will go further back which is good for tall people.

Another thing is the fixing. S2 has 4 bolts and this linkage has only 2 located further back, but is easy to do the new holes to mount the linkage.

The last thing are the return springs. These linkages have no return springs because the ib5 has them internal, not like the bc.I Think the solution will be simply to make a external return spring setup.

The knuckles Jano mention are also a very good improvement over the standard ones made of plastic. This is essential to the feel of the linkage because all wear in the mechanism finally is transmitted to the selector.