Go to the Ford Six Performance site, then Advanced Search, and looks for threads by a member named Von Writter. He is building a full-size Fokker D-7 replica and getting ideas for powering it with a Ford 300-six. I think he is pondering a centrifugal supercharger, which would be pretty close to period-correct, and boost power-to-weight considerably, even at lower crank rpms. It does increase complexity, however.
Another member (who hasn't posted in some time) calling himself 6-Banger Bill was cutting up aluminum Chevy heads and welding them to make lighter, better heads for the 300-six. Now part of his goal was better port-flow and performance at higher rpms than we want an airplane motor to turn. But the lighter weight is certainly desirable.
Keep in mind (anybody; I'm not pointing at anyone) that an "auto engine CONVERSION" suggests, at least to me, something more than putting a car engine into an airplane with minimal alterations. The Ford Big Six was a capable auto engine right from the factory. It could be a relatively quite and reasonable engine for some kinds of airplane, like that Fokker replica, WITH a lot of upgrading and alteration. My feeling is that whether any particular engine was a good car engine is irrelevant here; the point is, can it be made into an acceptable airplane engine. The silliest piece of advice I ever read was by Richard Finch who suggested that you might see whether you want a particular car engine in your airplane by taking a test drive in a car that has that engine!
About crankshafts, the 300-six as used in bigger trucks and maybe some pickups had a forged crank. Again, search FSP for info on this.
An aluminum intake manifold, either the factory efi intake or one of the aftermarket intakes for carburetion, will save some weight.
