My outside power box with standard circuit breakers is inside the same box as my meter socket above it. But you don't need to remove the panel cover for the breakers to service the meter socket. So if a new meter socket for a digital meter (which the power company is forcing me to get) is sized for the old box, then should I need to replace the load center since the old breakers don't meet current NEC code (but wouldn't be touched)? And how likely is replacing a 1970 meter socket going to require more space (larger box) for new meter socket (i.e. is there some kind of "more space for wiring" when it comes to replacing a meter socket like there is for replacing a load center)?

The NEC does not regulate the breakers, other than to say they must be "listed" for use.

That work is done by testing agencies such as UL. The only issue I recall was with certain models of panelboard that were outright dangerous.

If you PC is going to replace your meter base and not involve the panelboard area then you should be fine.

Who said the panelboard and or the breakers had to be replaced because the meter base was being changed?

Do I understand correctly that "the box" that the utility meter
is in also contains your circuit breaker panel?
or are these two items physically separate...?

Yes, both the meter socket (in top half) and circuit breaker panel (in bottom half) are inside the same metal box overall. However, removing the front cover to lower half of the panel for the breaker panel isn't necessary to remove the meter itself. Changing out the meter itself does not involve opening the box (it's not an A-enclosure where their equipment is inside my equipment); it's locked using a metal clamp ring on the outside. However, I'm not sure if the meter socket can be detached and pulled through what would be a round hole in the front of the top half of the box... if the meter socket has a square base instead of a round base or if the wires can be detached. This whole box for both may have been one kit when originally installed.

This is my main concern: I've read that new digital meters have prongs whose separation may not be the same distance as the analog meter prongs. I'm worried my old meter socket might not make good connection with the new digital meter prongs and cause arcing. The power company doesn't care because the meter socket isn't their equipment and their contractor is going through the neighborhood "hot-swapping" the meters without even turning people's power off first much less checking the meter socket for wear of the contacts. So I guess I'm wanting to know how likely my 1970 meter socket (Zinsco if it's the same as the load center) made for an analog meter is going to meet the tolerances of distance between the prongs of today's digital meter--which I think is going to be an Itron?

Thanks for reading,
Morty

Contact your utility company. If the meter base needs replacing to accommodate their meter they should do the work or at the very least supply the meter base to you.

Here in Tidewater Virginia, the power will supply the base at no cost, however, the installation of the base is the responsibility of the customer.

In my situation, my meter base needed to be replaced. The utility supplied the meter base to me, then cut the power to my home and notified a city inspector that power had been cut.

After I installed the meter base I had to call the inspector in order to get an inspection and a certificate faxed to the utility authorizing them to reconnect the power to the house. Fortunately for the whole process took less than 2.5 hours.

Morty,
I get it, you're concerned that a 47 year old combo meter / panel will safely accept an updated utility meter.
If I could see the condition of your equipment I might have an opinion, but I will say that we have replaced meters from the 1950's and newer with new utility meters and I have never been advised of a problem or failure.
From the utilities point of view if there have been problems or issues I would think they would have reacted as meter failures do mean liability on their part with negative publicity and lost revenue they don't need.
But don't take some guy on the Internet's word, hire a professional to take a good look! you may sleep better...
Sincerely,