yup does involve some modifications to the legs underneath youll need to be good at welding.
you need to place the seats in the car and line up the bit in the centre of the 2 runners youll notice one is in the right position but the other side is to far out requires eitehr removing and welding the legs back in the correct position or just softening the joint up and pushing it into position.
simpler way is to take the mk3 seats and mk1 seats and use the base from the mk1 seats on the mk3 seats i think there is a guide somewhere someone may have a link.