Most likely a V32 with 8” pistons.
Heh. Largest single diesel prime mover I’m aware of is General Motors’ Electro-Motive 645 V20, which appeared in only a few locomotives (the SD45, SDP45, F45 and FP45 series) but had crankshaft problems. (The “645” stands for 645 cubic inch displacement per cylinder, so the 20-645E3/B would have a total displacement of 12,900 CID; bore is 9 inches and stroke is 10 inches.)