Most recessed cans accept standard trim rings...go to Home Depot and buy one that you like, bring it home and see if it fits...usually no need to replace the installed can if it still works. If they are old, non-insulated cans, there are insulated 'domes' that you can place over them in the attic. We have a number of cans in our new house and use CF floods in them. Plenty of light, less heat and lower electric bill. Cans are currently in favor so I'd think twice about removing them.

Recessed cans were not in vogue in the 60s so they were probably installed later. Remove one of the floods and see how the trims are attached and remove one of the trims to see if there is any indication of the brand. The trims are usually held in place with springs. As an example, the common brand at the big box stores is Halo and new trims are easy to find.

Since you are removing the popcorn ceiling you will need to remove the trims any way so you can take one with you in your search.

IF you chose to remove the cans, then your are left with the problem of replastering the holes and doing something with the wiring.

You have several options and considerations.
The wiring, although appearing old and dilapidated, may in fact be just fine. Determining the condition, is to understand the products evolution.
The cans can be cleaned and the trims replaced as well as reflective inserts.
Are they presently dimmed or do you intend to use them as such in the future?
The lamp selections are incandescent (no longer mfg. for sale in the U.S.A. after 2012), halogen, also an incandescent, CFL's and encapsulated CFL's. Both contain mercury, both are not mfg. in the U.S., in CHINA.Both are available dimmable.The most recent in the evolution of residential lighting are the LED. Although the initial cast may seem excessive, do the math. the power consumption, per fixture is 12watts, the bulbs have a life expectancy of 18 to 30 years, and they are dimmable with no special adaptation needed.
Thats your 6 fixtures at full brilliance for the same cost as a single 75w incandescent bulb, or 3-100w CFL's.

Actually the bill doesn't eliminate incandescents, it just says that by 2012, lights will have to be 30% more efficient, and by 2020 70% more efficient.

An excerpt from the Energy Star site:

"ItÂs not entirely correct to say "CFLs will be required" or "incandescents will be phased out" because the standards set by the bill are technology neutral, and by 2012, a next generation of incandescent bulbs could satisfy the 30% increased efficiency. There are also other lighting technologies, such as halogen and LEDs that will be able to meet the new requirements and are expected to both increase in performance and drop in cost over the next few years.

So hopefully we will have more options than ever by then.

"twobengalsandme"
The LED is already here and has been used in commercial applications for some years. They are dimmable, white light, cool operation, meet CA title 24 and have a usable life of 18 to 30 years.
All attributes which cannot be found in halogen.
Its not 2012 yet, and if the liberal, eco-nazi, dismalcrates continue, we'll be living in caves with blackout curtains to hide the candle we use to cook with.
Watch metal halide to replace halogen.
If CFL's are the least expensive option to meeting those standards, as they currently are, they will not need to be "required". None the less,CFL's and encapsulated CFL's, both contain mercury, both are not mfg. in the U.S., in CHINA.

"snoonyb"
Jeez, don't get your panties in such a wad. I merely quoted a paragraph from the Energy Star website. I didn't even mention halogen. And I could care less if LEDs meet CA title 24, so I went with all incandescent, except for the low voltage halogen on the monorail over my island.