The Pinto has no "frame." It is a uni-body construction. So, either you take the whole body structure with the floorpan and its theoretical "frame," or you had better weld up a rather strong roll cage supporting all the load points (which is not very practical and likely very expensive).
If the car is a 71-73 it has mounts for the 1600 and 2.0 engines. A 74 has mounts for a 2.0 and a 2.3 (which are mounted differently). 75 and up had mounts for the 2.3 and the V-6 ( 2.6 or 2.8 ). I do not know if the inline 4 cylinder and the V-6 mounted differently. I'm not dead sure on the 74 and up cars, but I'm close.
Honestly, if the car was free, and ran, perhaps you could pull the doors, jack up the springs and run snow tires and have something mildly fun for gently off-roading. Otherwise, there are other vehicles far better suited for becoming a "dune buggy."