Timing Camplate On Pre Unit Gearbox

Hi Guys I'm restoring a 1948 Speed Twin T5 pre unit , I'm confused over the different positions of setting the Cam plate in the gearbox the Haynes manual said in 4th gear you tube video said neutral but both seem to jam up when I've got them re assembled , I've tried several different positions & checked the cam plate is in 4th or neutral any help woul

 

Thanks for reply, mines a 500 1948 its slightly different but it was helpful ,I think I may be getting some where the video I've seen shows assembly with out kick start on , the main shaft after the cover was tightened up wasn't coming through far enough to put gear on so I've tapped it through & I now have some of the gears & neutral so will try to set up selector fingers crossed will keep you posted thanks