There are a number of kits on the market, from various suppliers. You say that the car has '126' wheels, but which suspension units do you still have on the car---the kits ARE different vis-a-vie 500/126, mainly the adaptor plate which is different. You will probably find that you can get away with retaining the original master cylinder (although you MAY have to go down to the smallest rear wheel cylinders--5/8in). I would also suggest that at the same time you change the 'rubber' brake hoses with 'braided' hoses--they do help to improve the pedal 'feel'.