Hi
You will need to drill new holes, unfortunately. So what kind of parlor guitar do you have? Is it just for playing? Any sentimental values? Any historical values? What kind of shape is it in?
As long as the wood is in a good shape, drilling new holes won't affect the guitar. Most likely, the old holes will be covered up - if not, you can plug the holes and add touch-up paint and they will be almost invisible. Drilling new mounting holes can be tricky but if you take time, it's not bad. Or, you can take it a competent repairperson. Probably a one-hour job ($60-$80) plus new tuners.
I love old parlour guitars. They got unique sound and the mojo!
Cheers
Chief