Mate ! I would start looking at the crank pulley off a 1G-GZE and see how hard that might be to adapt to your 18R-G unit. That means that you can still keep the S/C clutch, but you would have to get the distance/spacing correct and then hope that a 5 rib belt of the correct length is made and available to you. Dayco was my friend here when I replaced the belts on my GZE motor. Perhaps you can adapt an air con pulley or, thinking laterally, get a 3 rib crank pulley and use the centre 3 ribs of the S/C pulley - but that might be a bit Dodgy Brothers engineering.....