Some cars leave a paper trail; the Ferrari 312 P left a name and a place in Ferrari's list. What follows is what can be said with a source behind it. Its designer of record is Mauro Forghieri / Giacomo Caliri / Gioacchino Colombo.
Where it came from
The Ferrari 312 P was a Group 6 Prototype used for racing in 1969 and 1970. It used a V12-engine derived from the F1 car Ferrari 312, detuned for endurance. When the F1 car was fitted with a flat-12 engine with lower center of gravity, called boxer and marked Ferrari 312B, also the new 1971 version of the sports prototype came with the boxer engine, thus the Ferrari 312 PB is the successor.
Under the skin
it is rated at 331 kW @ 10,800 rpm 465 N.m. Kerb weight is 585 kg. Power-to-weight lands near 566 horsepower per tonne, which is hypercar territory, where the limiting factor is the tyre, not the engine. The wheelbase is 2220 mm. These are manufacturer figures carried by Wikipedia and Wikidata, not road-test measurements.
In context
Where it sits in Ferrari's history is not in doubt: the Ferrari 312 PB followed it. Nearby in the Ferrari catalogue sit the 250 GTE and the 328 GTS.