I built a gun under a Colt Conversion Unit back in the early 90's. I still own and shoot that gun today, infact.......it's a favorite for me, both at the range and in the field.
Re: the Bushing, DON'T use the Collet bushing. The step at the end of the CU barrel is too short, and you won't get the benefit of the collet on the barrel.
Buy a "Gunsmith Undersize/Oversize bushing", and fit it to the barrel, and then to the slide. It's easy to do with emery paper, and a wood dowel.
Re: Recoil Spring.....I did a lot of experimenting, and to get the best accuracy, I now use a std 16 lb 45ACP recoil spring in an attempt to slow the slide movement....yes, my slide locks back when it should.
My CU will pretty much "Hold the Black" at 50 feet, and does the same at 25 yards on a 50 yard slow fire pistol target.
Re: ammo.........I also think the copper clad ammo is a benefit.
Re: The 2 pc chamber.........the copper clad ammo extends the cleaning schedule, but I haven't decided if running it dry is better than a grease or a lubricant.....Maybe I haven't found the right lubricant?
CU pistols are a "Hoot to Shoot", and they can help to make you a better Bullseye shooter, if you work with them.
I've used mine in the woods for Squirrels, and don't feel I need more accuracy...........but it would always help.
Enjoy your New Toy.
Tom