Also, Don't overlook the Seagrave / American La-France / Pierce Arrow V12's for inspiration. They tried some really unique setups, like in the 906. Is this a OHV, or a flathead???
Just a note: Seagrave introduced their 906 cubic inch V12 engine in 1931, and Pierce Arrow's V12 at 398 cubic inches wasn't in production until the following year. This makes for a curious thought of who may have copied who; but I believe that I remember reading somewhere that perhaps Seagrave had investigated, or perhaps were courted by Pierce as an engine supplier, but after realizing the engine, although a V12, was still not of sufficient capacity for their big fire apparatus, Seagrave may have "barrowed" some of Pierces' engineering witnessed to produce their own more suitable example and at a cost savings vs. purchasing such from Pierce.
Later, (1938 +/-) after Pierce Arrow faltered, Seagrave purchased the tooling for the Pierce V12's then having been produced in 398, 429 and 462 cubic inch capacities and set off with the Seagrave 462 and 531 cubic inch models used in the smaller fire apparatus examples with some re-engineering making the engine series more suitable for their needs.
There, more useless information for ya!
Scott.
B.T.W., which engine is in the picture?