The rifle was FTR (Factory Thorough Repair) likely shortly before it was sold out of service.
During FTR, every effort was made to bring the rifle to "new" condition. This included the fitting of bolts with head numbers as low as they could manage.
Given that bolt-heads were numbered 0, 1, 2 and 3, it is likely that your rifle would work with a 0 or a 1. A 2 was about the highest they would pass out during FTR because that gave them only the 3 before the rifle had to go back for FTR again.
Bolt-heads differed, supposedly, by about 10 thou apiece. Modern ammunition is sometimes so far from the original specs that it is possible to have rifle gauging PERFECT and still have 20 or 30 thou headspace OVER MAX. Remember always that the .303 headspaces on the RIM. As long as the cartridge goes into the chamber and is held by the Extractor, nothing too terrible can happen. The paranoia regarding "headspace, headspace" is a result of the American firearms press and their constant ballyhooing back in the 1950s and 1960s about the wonderful .30-'06 and how incredible careful you had to be with it. But the '06 is a RIMLESS cartridge, and a faulty extractor can allow it to go into the chamber too far.... and the results can be disastrous. With the rimmed .303, you don't have this problem.
Best bet is to get a bolt, install it, make sure that the rifle will accept a round. Get hold of someone who has the range of bolt-heads. If the rifle will not allow a round to chamber, go to a lower number of bolt-head until you find one that WILL let it chamber the round.
To get the best-shooting ammunition for your rifle, handloading is mandatory. Wrap a pony-tail tie or a small O-ring around the base of your store-bought cartridges, just forward of the rim, on their FIRST firing only; after that you won't need it. This will hold the round central in the chamber and hold it back against the boltface at the same time. You end up with brass which is fireformed for YOUR chamber. Now you simply neck-size this brass, load carefully and you are on the road to building PERFECT ammunition.... for YOUR rifle.
Wish you were a few hundred miles closer; we could suss this out in about 15 minutes.
Good luck!