Probably off a MK2 or MK3. Worth fitting the master cylinder from the donor car as well. Improves the brakes a fair bit. I like to adjust the pedal position on MK1s. Doesn't change the braking at all but feels better underfoot.

If you look at the pedal you will find there is an adjuster off the back of it. I think it is a 15mm spanner to undo the lock nut. Then pop the pedal off the adjuster and wind the adjuster out a few turns. Re-assemble things and give it a try. If you adjust the pedal so that it sits just a touch higher than the clutch pedal, I found that to be best.

Gavin