Just to follow up...

I ordered some proper silver mica caps for the IFTs and that seems to
have made the difference. I had been tinkering around using ceramic
discs that I had on hand, replete with their long leads.

FWIW, I wouldn't have thought that the cap quality would have made so
much difference, nor that my one-inch leads would have terribly upset
anything but apparently so. Although the IFs tuned correctly with the
ceramics it did feel 'broad' and AM signals seemed broad on the dial
as well.

After installing the first set of micas it was noticeably sharper
tuning and while repeaking after installing the second pair the rig
popped right into oscillation as it should.

So my mystery is resolved and maybe this experience will assist
others. For reference purposes...and this may apply to other
Hallicrafters 1650 kc IF transformers as well, the mica caps I used
are 330pf and the coil range is in the neighborhood of 20-30uH, mine
were found ~27uH and the best measurement I could get off of one of
the bad original micas was 325pf.

73,
Bill W X 4 A