I have the feeling that a 33/67 split between West and East coast is somewhat right. In that way you’ll be able to get an advantage against the weakest power in the Axis side, Italy, and also threaten Germany enough that they’re unable to finish off Russia. The goal is to ASAP push Italy to 10 IPC income and Germany down to around 40 IPCs, at which time you’ll be at an advantage for some turns since all those Jap IPCs are still marching over the Asian steppes, whereas your IPCs are right in the thick of it.
In the long run, a chain of tanks and infantry pouring from Algeria and maybe South Africa will also be able to be used against the Japs around Persia. The trick with this type of play is to always be able to keep a fleet afloat off the West coast, either in a defensive stance or, if the Japs sail a lot of ships west, offensively. Obviously you then might have to spend 100% of your income on the West coast on certain turns if the Japs are very aggressive, but in the long run your spending should be more close to the 33/67 split. All of this assuming that the Japanese spend the majority of their IPCs on ICs, transports, land units and bombers to throw at China and India to break through vs. Moscow, which seems to be the typical Jap strat.