Hi guys!
In the previous post I just wanted to tell that the change was in progress, although the engine was not as healthy as I wanted, at least I know that everything works. 
Finally after all that I have been thinking about I got a 3sz that needs repair. While I wait for the grinding shop, I have some comparative photos. It’s something that I would have liked to find somewhere before doing it on my own. If it helps someone, I’m happy.
First a photo of the little engine (or what was left of it)
First comment that it is different from what I had thought. It is basically a k3 with the longest block. In my celica 77 I had done something similar (1.6 to 1.8) by changing the crankshaft where the stroke of the crank changed from 70 to 77 mm using the same block, but the 3sz is a longer block with longer rods.
Well, let’s go with the photos. The block apart from being longer, has oil sprinklers towards the pistons (my k3 does not have them), the mounting points are the same as in the old block.
Crankshaft: I thought they could be the same and that only the length of the rods would change, but they look different. They use the same main bearing. The connecting rod bearing are different.
Cylinder Heads: Look structurally the same. The intake ducts are obviously larger on the 3SZ. (My cylinder head is ported and it’s also 2mm smaller). The exhaust ducts look the same. Intake valves are bigger, the exhaust valves could be a little bit bigger or not, my eye is not that expert … The last difference I found is that the spark plugs are 16mm on the k3 and 14mm on the 3sz.
Cams: Very very different intake cams (my k3 is a k3-ve2), exhaust cams could have a little difference. To my eye they looked the same, but in the photos they look different.
Oil pump: they are different …
Rods: They are longer, look a bit thin (I was surprised by that). They use different bearing. The 3sz ones are a little bigger.
The piston of the 3sz could be used in a turbo application, I was surprised how concave it is.
trigger wheel: they are different, you would have to exchange them if you want to use k3 electronics.
Well, as you can guess, I’m going to use the 3sz block with its cilinder head, but I will use k3 cams and k3ve2 pistons (I had the old ones from sirion stored). I don’t dare use the high compression pistons.
Finally, for the intake I’m preparing a four throttle since the engine I bought came without the intake manifold. (is of Yahama R1).
I hope it helps someone and sorry for the post so handmade, without using professional measuring tools.
Bear hug!