This is a wonderful rifle made by your grandfather. I would learn to reload for it.
A chamber cast would be a good first step because calibers like 7mm Ackley are often made by a variety of slightly different non-standard reamers. So, I would:
Get a chamber cast made.
RCBS either makes dies or made dies. Call them with your chamber cast, a set of calipers and discuss with their technician if your gun is a good fit to their dies? You're probably GTG, but maybe they need to remove material from the bottom of the die or something. They may ask you to send the cast in first.
Also, check out(call) Huntington Die Specialties
they can help you get setup loading for this.