Personally to get the revs out of it I would go longer rods...Like ABA. Bore that to an 83mm and pick-up a set of custom pistons (or put a 16v head on it and convert to solid lifter with 13:1 EurospecSport.com ABF pistons) Do cusom rods and a 1.8L forged crank and go to town. The motor should be able to turn 9-10K that way. Hit up the 280-290* cams in the .45-.48 lift range on the intake...Mebe upsize the exhaust valve a mm and you can get some more high RPM exhaust flow.