You do realize that is kind of like saying Ford truck, there have been a lot of different Oshkosh trucks built since 1917. I think at one time someone did offer a P-series cab in resin, but haven't seen one in a very long time so could be mistaken.
The P-series is commonly used for heavy snow plow trucks, it is mostly flat panels but at all kinds of wierd angles. The cab is wider at the top, than the bottom, and gets wider front to back. The front and side windows angle out from the top to help keep snow from sticking. These things make me think it would be a really tough job to cast correctly.
I was sketching one out from measurements so I could try and scratchbuild one, but that project is a long way off.