Great photo !
Karl, if you do it in 1/48th scale, then you'd just need code letter and serial number decals, available as sheets with all letters / numbers, from Hannants - code letters definitely on Xtradecal sheets X023-48, 24" and 30" Sky Code Letters, and serials from either Xtradecal (if they still have them), or Tally -Ho, and others as well. If stuck for serials, then Xtradecal sheet X72157 (72nd scale) has black numbers / letters that are usable in 1/48th scale.
For 1/32nd scale, you'd just need the serial number decals, with Ventura sheet V3270 being a good choice.
Not sure if MJ318 had the nose art and 'City of Oshawa' though - the name suggests a 'Presentation' aircraft, so if it was on another airframe as well, it would probably be 'City of Oshawa II'. for example.