[PeterN]

Thanks for all the responses and advice.

I decided not to grind down the "lip" on the line cord hole for a "Heyco" style strain relief. I was concerned with all the metal filings getting into places hard to remove. Even if masking off everything in the underside of the chassis.

What I did was to design and 3D print a replica of the original Philco molded on strain relief, in ABS plastic. This will get glued on to the new line cord with either thick Super Glue or epoxy (it is already a snug fit). The strain relief will get hot glued into the chassis hole, with a "ty-wrap" behind the chassis for insurance against pull out. This way the line cord could be removed in the future.

Attached is a picture of the new strain relief.