Except the 1500 spring is not long enough to hook on to the slave cylinder ‘eye’. I found this via Google....
https://www.tapatalk.com/groups/xweb/clutch-pedal-spring-to-use-or-not-to-use-t8988.html
I modified my slave cylinder set up as suggested in the article below from C. Obert & Co site ( formerly Fiat Plus) but I think you should keep the spring at the pedal.
I actually used the 1500 spring with stainless steel wire loop to adapt it to fit. Otherwise it would have been too short! Works just fine but looks a bit amateur.
There are other useful tech tips on Chris Oberts site
http://www.fiatplus.com/index.htm
Tech Tip for November 1998
Springy X1/9 clutches
Taken from Volume 2 Number 3 Ciao!NEWS Winter 1996
The 1500cc X1/9s came with a bigger clutch than the 1300s and a new starter. In an attempt to modernize, a self-adjusting clutch design was used that actually keeps the throwout bearing touching the pressure plate fingers, which unfortunately causes premature wear on both the bearing and the plate. Fiat Plus has converted many of these back to pre-79 clutch systems.
The 5-speed X1/9 clutches tend to wear out quickly as the throwout bearing remains in contact with the pressure plate fingers. On 5-speeds, the clutch return spring goes from the clutch arm at the top of the transaxle to a small metal bracket fitted at one of the engine-to-transaxle bolts. On the 4-speed SOHC, the clutch return spring goes between the arm and the clutch slave cylinder. By converting your 5-speed to this 4-speed style spring mount, your clutch will release completely and should last longer.
Of course, the new design was to prevent the need for clutch adjustments. Thus the obvious downside of this conversion is you will occasionally need to do just that: adjust the clutch pedal freeplay. You can usually feel the freeplay with your foot on the pedal--it should be no more than one-half inch. Just remember to add the adjustment procedure below to your regular maintenance schedule, and/or when you detect the freeplay decrease or disappear.
The best way to prepare for this conversion is to get ahold of, or at least examine, the setup on the 4-speed before it's disassembled. You will need to use the 4-speed spring (the 5-speed spring is the wrong length) and you'll mimic the 4-speed's mounting setup on your 5-speed.
Here's how to convert the spring and adjust your new old-fashioned clutch:
Move the coolant overflow bottle out of the way if it blocks access to the clutch release mechanism.
Remove the small cotter pin, washer and lightweight or "weak" spring mounted on the clutch release shaft on your 5-speed.
Remove the 5-speed spring. Install the 4-speed spring, mounting it on the clutch slave cylinder as it was on the original 4-speed.
Adjust the clutch so that once the piston-to-plunger clearance is gone (this should be almost zero anyway), you have one-half inch freeplay at the top of the stroke.
Reinstall the cooling bottle if necessary, and bleed the cooling system as described in Ciao!NEWS Vol. 2 - No. 1.
Step on the pedal and you're out of here!
