I'm thinking of buying a new electric vehicle (EV) and adding a 50A 240VAC/3W to my garage for the charger. The electrical source would be the existing 1975 vintage Cutler-Hammer CHP loadcenter that is also the existing service panel. A 200A 120-240VAC/3W service powers the split-bus (copper) loadcenter, with a 60A/2P main breaker for the house loads and two empty 2-pole spaces for two additional main breakers on the service bus. The panel is clean and appears to be in good condition. The new breaker would be CH250, 14KAIC safety breaker.

My homeowner's insurance company informed me that when an electrical system in the house reaches 40 years old, insurance rates increase because of added fire risk. Replacing the electrical equipment would avoid the increased premium, not to mention the cost of replacing the electrical system.

Question: In your opinion and experience as electrical industry professionals; 1) is it safe to add this circuit to the old panel, and 2) are there other considerations I need to address in my planning?

It really depends on what they consider "the system". Are they really just saying the load center, maybe just the breakers or they might mean a total rewire. That is a question you really need to understand.
I would want some clarification but my guess is they are just looking for a way to cancel you. Insurance has gotten crazy in the last few years and companies are doing irrational things.
As for your situation, if you have the slots I don't see a problem using that panel. The real question is whether you have done a load calculation. That would be the first thing I would do. Car chargers are continuous loads and you need to be sure you have the extra capacity..

OK, IMHO here goes....

IF you will only have six (6) handles that cut the service to your dwelling when you add the 2 pole cb for the EV charger feeder, you have NO NEC situation.

However, as Greg said, a load calc should/must be done to assure that the main service conductors are sufficient.

As your profile here says you are a PE/EE that should be no problem. You said that a 60 amp 2 pole feeds the house loads, and I'll guess you have HVAC and 2 'other 2 pole cb in the 'main' part of the split bus section.

As to your insurance co. request, do you have anything in writing, as to what they call 'electrical equipment'?

Perhaps, a new panel and AFCI breakers/GFI and a SPD ?? I can't see how they could say a 'rewire'! Maybe they would like a copy of any permits IF you had any electrical work performed??