Trying to keep it as original as possible... I'd like to carry both a front & rear spare tire because I drive it., Is there a rear end or running board mount that would be an original type for 1915 to handle this?

Thank you!

You would still have to demount and mount the tire along with replace/repair the tube, then blow it up. You can't install a clincher with the tube inflated.
That being said, Google "mtfca; spare tire running board mount"
There have been a number of postings on the subject.

I've seen some people go so far as to have a spare front wheel and a spare rear wheel mounted on the running board. I carry a spare tube or two, but if a tire blows out and rolls over the cliff into Bottomless Canyon that's not going to do me much good.

Hi Tom,

For most folks, just carrying a tube of each size and, of course, the necessary jack, tire irons, and a tire pump is adequate as rarely does a tire casing fail catastrophically.

Back in the day tires were not as robust as they are now and the road conditions were quite rough on tires. Motorists did often carry a tire of each size on the running board.

My '14 touring came to me with a twin tire carrier installed by the original owner.

The tubes I bought most recently are for both 30 x 3 and 30 x 3½. That's handy.

Tom, a few cars in Australia have turned up with blacksmith made period spare tyre mounts at the rear of the car.
The basis of the carrier is a ring of bar stock about 24" in diameter. To this are attached two arms which are bent to go up to the top brackets. The L arm of the top brackets is flattened at about the centre and drilled to take a bolt to hold the two together.
At the bottom, a similar bar is connected to the rear spring/chassis U bolts.
The tyres are strapped to the carrier as required. While not factory made, it is a period method to overcome a problem. On Canadian cars it still allows use of all four doors.

Hope this helps.
Allan from down under.

Gemco made a rear tire carrier that held two tires. My father owns one. (They also had single tire version.) You remove the stock rear spring clamps (u-bolts and straps) and mount the tire carrier which had its own u-bolts in their place.

See the two tire example here:

http://www.mtfca.com/discus/messages/118802/123629.html

Gemco also made a "basket style" rear tire holder the accommodated two tires.

I have a 1916 Gemco catalog but I'm too lazy to scan all the pages of the various running board and rear tire carriers - both Ford and non-Ford.