Running on Unleaded can be done for miles before valve wear occurs. You may find you need to adjust valve clearances more frequently as time goes on. As for conversion 'Turner Engineering' and 'ACR' produce remanufactured heads for unleaded at £300 up exchange. I fitted stage1 8:1 but in hindsight wish I had spent the bit extra and gone to stage 2 9:1 (increased BHP). It depends what you use vehicle for. You could carry on with additives but this kind of avoids the point of 'greener?' unleaded fuel.