[Ron Ramirez]

The IF transformer consisted of two tuned circuits which are resonant @ 175kc

260 kc in model 91.

<Hopefully, would like to find some one who sells new old stock.

GLOM

I'll ditto that. Good luck finding a NOS coil, which may have the same issues due to the nitrocellulose insulator used between windings, which breaks down and causes the windings to corrode. You're better off rewinding the coil yourself, or finding someone to rewind for you.

< If I leave the shield off, I am concerned I might well end up with motor boating.

Yes, it will squeal and/or motorboat without the shield.