What Pete said regarding the blocks.
As to your other question, yes, the PK 3500 C floats perform MUCH better than the A and B model 3500s. The floats are really very different in design, with less V to the bottom, wider decks (if I recall).
I flew a C 185 on the early model amphibs for several hundred hours. It was a humbling experience, but a good learning experience. You really have to be on top of your game to get those early floats to perform, and loads are critical. Essentially, you spend a lot of time praying for wind. I flew one 206 on these early floats and a friend mentioned to me one day after watching me depart: "You know, if it barks like a dog and drools like a dog, it might actually be a dog." Best compliment that plane got.
In 1986, I was given the keys to a brand new 185 mounted on late model PK 3500 C floats (straight floats). I groaned, but as I gained experience with the floats, I began to realize that their performance was MUCH better than those 3500Bs.
ten years later, I parked that plane on a mountain after the crank broke. The replacement 185 was equipped with EDO 3430 floats, which had always been my favorite float on these planes. I quickly realized that this plane got off the water with the same loads in almost exactly the same spot the plane with the PKs did.
The key with the PK floats is learning to fly them. The sweet spot on step is very narrow, and can be hard to find and hold initially.
But the PK 3500 C floats are good strong floats with good performance.
MTV