[Mondial]

The HV windings on both replacement transformers is a bit low as I believe you mentioned you measured 700 VAC on the original transformer. The bigger one is closer at 600 VAC, but otherwise larger than needed for the actual load.

You also mentioned that your speaker field is a bit lower in resistance than the original, so you might have to take out the added 250 ohms, giving you less voltage drop which would compensate somewhat for the lower HV. You could also increase the capacitance of the first filter capacitor which would increase the DC output voltage a bit.

I would try isolating the shield and reinstalling the original transformer first. I doubt you would notice any appreciable difference in reception with the shield left insulated and floating with respect to ground. At least you would be able to measure the actual operating DC supply voltages which would give you a better idea of what transformer you might need to order.