My cars a 1.4 8v. I don't know if the pedal will be longer travel with just the GSi brakes on. Mine has 4-pots on the front so I'm expecting a bit longer travel anyway. I think Olly Hewits car was a 1.4 and he has fitted GSi brakes to that. Might be worthwhile contacting him to compare notes.
The master cylinder off a GSi will not fit. The GSi's were mostly ABS models and the master cylinder is different on those. Although if Johnnys has ABS it may fit.
Check for other problems first, ie. brakes are bled properly etc.