How can I adjust wheelbase?

The factory bolts that secure the K have special conical shanks at the head end. As you tighten them, they draw the K into it's designed final resting place. Once the bolts are even just snugged, you can't move the K very far, certainly not anywhere near the distance you need. I would just pay the alignment guy the pocket change he wants, just to tell you what is going on. You can spend an entire day stringing the car and not know what 15 minutes on the rack can tell you.
But if you don't have those factory bolts, well yeah if you push one side all the way to the front and the other all the way to the back, then things can get crossed up. You need those factory bolts. The torque you put on them is not designed to keep the K from moving, only to keep the bolts from coming loose. Remember; ALL the forces that the front tires see, get into the chassis thru those 4 bolts. If the K slips on the road somewhere, at speed, that could really ruin your day; make sure the factory bolts are in there.
A similar thing is going on in the rear;ALL the forces acting on the rear tires get into the chassis via the front eyebolts. There are two sizes of bushings and IIRC each takes it's own bolts. In either case, the bolts have to be a tight fit inside the bushings and in the perches. The torque you put on those front eyebolts, again, is just to keep them from coming loose; the actual locations are engineered by the parts used.