First welcome to the site hope you find the information here helpful in your efforts related to factory original details.
Sure many of the early car member will know some of the vehicles that air cleaner was originally installed on. Have seen allot of them swapped onto early Mustangs over the many years of ownership. I recall them on some falcons and early Fairlane's I think
Here are some original air cleaners for you to compare from the cars production period
As far as where to go from here I would suggest that you make a plan as to where your going with the car, your resources, abilities and then stick to it. Changing direction/plans cost additional dollars and work in the long run.
A little original and a little modified is what allot of owners choose - just not our focus here. Lots of places have forums for those cars and they can help allot. Like many owners your first Mustang is often a learning project that gets replaced fairly early in ones ownership when you have learn allot more than your knew in the beginning
Just an opinion
Again Welcome