Puddin' Man wrote:

I have a 21 yr-old Cutler-Hammer panel that I installed myself back
around 1984.

No doubt there's numerous houses in which an interlock kit would
make sense. But there's nobody here but po' me, and, to my knowledge,
I don't need to idiot-proof the damned thang. Before any gas
generator were connected, the main breaker -would- be switched
off. And it would stay off until the gen. was removed.

It's your choice. With my electrical utility, if you "tickle" a
lineman, they will stop work, trace down where the electricity is
coming from, cut your lines off, and you will NEVER get electrical
service again. It's a union thing. They will blacklist your address.