After repairing the broken former, regluing pads that came loose during experimenting, and discovering the Spec An is 4MHz off, the local Oscillator for the transverter is now running where it should be - 42Mhz.
Despite being fairly certain the series inductor is the same type as specified, and after removing several turns to get it to 10t, it still wouldn't oscillate correctly. I then took it down to 5t and was wayyy over! So, a deft rewind, followed again by stripping off one turn at a time and testing, plus the expedient of changing over to the Frequency Counter from the Spec An, led to the discovery that free running around 42MHz needs 7t on this former. Adjusted to within a few hundred Hz, and took the shorting link out -Bang on!
Next step, then, is to build the Receive Down Converter. This is a simple NE602 circuit. The only down side here, is that other than feeding the Signal generator into it, I have no horizontal antenna for 4m with which to try and receive an off-air signal. I feel a halo or dipole coming on...
I still need to verify the instrument readings against listening for the oscillator on a GCR.