Late to the discussion (as usual) but congratulations anyway on a fine haul. Years ago my dad started out with a 450 and upgraded one or two features at a time until he decided to buy the 550 frame and do the complete upgrade... so he ended up with everything looking proper for the 550 (except the handle) with the proper auto powder drop, auto primer feed, and all.

Meanwhile, I still have all of the old, non-upgrade parts and have thought seriously about trying to buy the parts common to both models. What I have in mind is a dedicated press for one of my most-used calibers, probably 32 S&W Long. One item not mentioned, if you use either of the original Dillon (manual or automatic) powder measure, it is possible to add a post factory upgrade... a micrometer adjustment knob to the powder slide. This can be a useful improvement, particularly if you frequently change powders or charges in different loads. I have one on my manual measure and if I ever get off my lazy posterior and rebuild the 450, it will occupy the place of honor.

A random thought... I wonder whether it would be advisable to load 44-40s with black powder on the 450. I'm getting set up to campaign a Henry in that caliber in North-South Skirmish events, and that will require a fairly high volume of ammo between practice, individual events and team events. Has anyone loaded black powder cartridges on a Dillon Progressive?? If the plastic powder reservoir will be a concern, maybe that outfit that makes Pyrex™ replacement reservoirs would be able to help. Decisions, decisions.