How do I drop 19VDC from a 0-60VDC source to get an accurate linear 0-48VDC signal
If you're going to be wanting to log the data in the future, then I would assume you are going to need to feed the signal into an ADC for conversion into a digital form.

Because of that you might as well go that way from the start and not use the LM3914N.

You can scale and shift the incoming voltage so that the range you are interested in, plus the over voltage range, covers a range of (for instance) 0-5V (subtract 19V, scale the remainder down).

How do you do that?  This answer will probably help you: https://electronics.stackexchange.com/a/18265/4245 - subtract 19V from the incoming voltage using a suitable op-amp.  Then use a voltage divider to take that remaining voltage range down to the range of the ADC (3.3V, 5V, whatever).

You can then read the value from the ADC, log it, and display it on any LED display of your choice in any format you like, using any MCU that has the right IO options for you (the Arduino platform is a popular choice).

Once it's converted by the ADC you just have a set of numbers.  It's then largely up to you how you divide those numbers up.  Depending on your scaling resistors, ADC values (say, for a 10-bit ADC) from 0 to 900 could be 0% to 100% (19-48V) and displayed on an LED bargraph.  The remaining 901-1023 would be "overvoltage" and could trigger a different LED to start blinking as a warning...  The world is then really your oyster.