[Mondial]

The reason that your dial calibration moved by 20 kHz is because your IF moved up by that amount.

Now that your IF is at 260 kHz, you need to adjust the osc low freq and high freq trimmers to recalibrate the dial and restore tracking with the ant and RF tuned circuits. It should track the calibration of the dial more precisely now with the correct IF. Someone in the past probably aligned the stages with the IF off freq and compensated with the osc adjustments. What you have now (digital receiver) is more accurate in freq calibration than what was available 60 years ago.

When you adjust the osc low freq trimmer, rock the dial around the freq of a station near 600 kHz and find the setting of the trimmer which gives the best signal strength at or near the proper dial calibration. What you are trying to do is get the RF and ant stages tuned to track the osc at that RX freq. Since the ant and RF stages are not adjustable at the low end of the band, you are compensating by adjusting the osc to match their fixed tuning.

If after optimizing the response at 600 kHz the dial cal is slightly off, you can loosen the dial setscrew on the cap shaft and correct for it. Then go up to 1400 or so and set the osc high freq trimmer for accurate dial cal. The low and high freq osc adjustments interact so you may have to repeat them. Then peak the RF and ant trimmers for max signal at 1400. This should get you very close to optimum alignment and performance.