Campagnolo Syncro shifters - Pull ratio

[Kingswan]

I have a pair of Campagnolo Syncro shifters, they are 8 speed but i want to use a 7 speed block. Do I need to change the insert to a 7 speed or will the limit screw on the rear mech prevent the 8th position?
Is the pull ratio the same on 7 & 8 speed Campag downtube shifters?

Do I need this part??

 

[hamster]

Campag 7 and 8 both used a 5.0mm pitch, unlike Shimano (4.8mm) so you should be fine by simply having an unused and unobtainable click.