63 was a transition year and yes you have the long tail housing transmission which is the same length as the OD. Most 63 through 67 6 cyl trucks had the short housing. You don't need to modify the driveshaft. It looks as though your truck has a floor shift. This could be a problem with the overdrive as there will be interference between the the solenoid, speedometer cable, shift arms, and the shifter itself. It may be easier to locate the column shift components than to find an "overdrive" shifter assembly. You may be able to use the existing one with some modifications and relocation.
Fred
