the right spur gear for mod 1 11t & 13t ?

Hey guys the natinals is over and i did 2nd in qualifying and 2nd running during the 1st heat and didnt get to finish because my pinion"s grub screw was gone again with super glue holding it already. tried to solder it but last only for 3 min. so ended up not even getting points. anyway getting back to my question right nw m geared with 66/18 and m wanting to change my pinion to mod1 cause it could fit the 5mm shaft of my 9XL. So i need SOME HELP here cause m so frustrated today. would appreciate some suggetions on whats the perfect gearing. i already have the MOD 1 11&13T pinion. also what spur will match with my existing pinion and what brands couls i get.