Thanks very much to everybody. Disk controller is working ok now....
 

 Not sure what fixed the problem (may  be a compund)

- Implemented exact seek times.
- Got all the floppy lines from the "virtual" floppy
- Reimplemented the track functions.
- Implemented CRC calculation.

It's possible but it's not that easy, doing an FPGA implementation is much easier than doing an actual chip replacement
To do a real chip replacement needs a lot of extra work.

I think the main problem is to "tie" the modern technology with the old. The two devices behave the same on video or sound, but they are very different inside.

Kyp says that FPGA is easier, I think because in some way it is schematic. But he also says that a physical device made of real components can be created with the information. After all what he manages to design a FPGA core is a hardware descriptive language.

Imagine the possible turnarounds taken by the designer to make the chips real on the 80's, It can be that the contemporary FPGA circuit doesn't need so much pins for Dave and Nick, but you still need all the signals to "transplant" the hypothetical clone chip to the real Machine, to be able to return it to life...

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I am not the best source of FPGA knowledge, sorry if I can't give a better explanation.