Parts specific to older S&W K frames?

[65k10]

I recently acquired a couple trade-in S&W Model 64. One is a 64-3 (but doesn't have a pinned barrel) and a 64-5. I was kind of surprised to read some of the parts for these are already out of production, but beyond the hammer nose I haven't been able to figure out what important parts are specific to these guns. I don't expect to use either all that hard, but if there are any uncommon parts I might need I'd like to get them now before I can't get them later on. Plus, I'm also trying to decide if it would be worth grabbing a few more, but I'd like to make sure I can keep them running.

[JV_]

Some parts are available here:
http://www.gunpartscorp.com/Manufact...64-3-36815.htm