1.) Yes. The endurance package was introduced as dash 2E.
2.) Yes, except the triggers are interchangeable and S&W started using MIM triggers in some models while they still had the older frames.
3.) Yes for the first half then no for the second half. Forged hammers and triggers were not through hardened. They were case hardened. While it has been posted here that a thicker layer of their surface is hardened I'm not sure about MIM hammers and triggers.
4.) MIM hammers usually do not include a firing pin so they do not fit in dash-4 frames. Older style hammers with a pivoting firing pin do not fit in dash 5 frames. It used to be true that all forged hammers included a firing pin and all MIM hammers did not.
5.) (regarding the power port revolvers) The only dash 4 and dash 5 629s that are not drilled and tapped for optics would be fixed sighted revolvers if there are any.
I like the appearance of forged hammers and triggers and after my eye sight diminishes in old age I might want to put optics on my longer barreled 629s so for longer barrels my first choice is dash 4. Since I prefer flash chromed hammers and triggers and I'll never put optics on snubs my first choice for snubs is dash 3. That's theory. An individual 629's action, especially early carry up, usually is more important than its dash number. The exception would be long range accuracy. To pursue bench rest shooting or silhouette matches I'd insist on the endurance package for its tighter cylinder throats and smaller forcing cone. I actually bought 629s I found at good prices. If price does does not matter pick a dash number after evaluating which features are most important to you.
