Depending upon the number of new circuits needed, and the cost of a panel change (does it involve the PoCo and Inspector) the cost of two or three Stab-Lok FPE breakers may offset an entire Murray Panel with Breakers. I've seen them quoted upwards to $50 to $80 for used single pole 20A ones.
I did do a simple experiment involving loads of 200% of a CB rating (40A on a 20A CB), to have the upstream breaker (SQ D 30A and a GE 30A) trip first. I didn't do any bolted fault tests and don't want to even try without arc flash protection. I've heard that some will not trip even bolted.
My mother's dryer cord burned to a crisp when the thermal overload failed in the dryer convinced me to change her panel a few months ago. A typical "no trip" situation being a 120/240V circuit and 2 pole CB.
Be very afraid...
