If you find a period correct dial in good condition, it would only detract marginally (if at all) from the overall value of you have it installed. The issue is that an original dial will be very difficult to find and very, very expensive. Several thousand dollars.
Personally, as it’s your fathers watch I’d be tempted to leave it as is. After all, in all likelihood, this is the dial that your father looked upon for however many years.
Yes it’s not as valuable as an original piece but you will only increase the value by the amount you spend on a new dial anyway.
