The best place to find out about anything CZ is on the CZ forum on Rim Fire Central.
I'm not sure why you'd want to thread a 455 when there are so many 452s and 453s still out there, which are generally a bit more desireable IMHO due to the presence of 2 locking lugs AND the barrel attachment. The big draw of the 455 is the multi-caliber capability. I bought a 455 .22mag and added an LR barrel. Nice rifle, but accuracy was only so-so and I had feeding issues with the LR. Both of those problems could likely have been addressed by judicious application of a torque driver and a little twiddling of the magazine retainer, but for me that takes it out of the "easy swap" category. Others may feel differently. I bought a 453 .22LR and am pretty satisfied overall.
The other reason to consider a 455 is that you can easily replace the factory barrel with a high-end tube from Shilen etc. That makes more sense to me, except that you will be getting pretty close price-wise to a good, used, Annie, Cooper, or Kimber. Think carefully before you start buying stuff, lest you end up spending a lot of money and still end up less than happy.
