Your questions stimulated me to research my owner's manual (reproduction) for my '51 3100, as well as my Salesman's Truck Data Book for 1951 (original). Interestingly, I could not find reference to using a jack, where it is stored or even whether it was standard equipment. The sales data book lists: Tool Box--Under Seat, 50" x 19 1/2" x 6" for just about every model, meaning that space under your seat, which is the natural place to put a jack, handle, spare tools, etc. I recall questions on this board a few years ago about what is the right jack for a given truck and given the lack of factory information or photos, one can understand why so little is known about what is correct for the purists.
