I found a very interesting page from Internet:
http://users.ntplx.net/~kinukoyc/NewFiles/TCR%20Page%203.html
A lot of information about original Abarths. Good pictures.
There is making instructions for 5-speed gearshift console, fits also to 4-speed gearboxes. I made this system and it works much better than original Fiat 600:’s gear lever. Highly recommended!!! :)
http://users.ntplx.net/~kinukoyc/NewFiles/Shifter%20mech.html