If it's connected to other things, it
must have isolation. If it's going to be a self-contained and fully insulated instrument, get it working using a low voltage AC source to start with then change the input scaling resistors to suit the final voltage range.
Isolation without a mains transformer can be done using isolation anps and a miniature DC-DC converter to run them.
eg
And something like this to power the input stage:
There is an article here which includes measuring AC powerline voltages with ICs such as that: