I will need your model number CHXXX-XXXX to give you the right rebuild kit to order. Then I need to know the hours for each motor to determine what if anything else needs to be done while you have the jugs off, like lifters, valves, mechanical fuel pump, etc... I'm going to assume a lot from experience below.
My guess is that you are blowing oil like mad to the back of the motor and to the fuel pump side, with some coming from the throttle choke area? Starter side of the motor is not seeing a lot of oil... Just a guess.
If you look under the air filter assembly when running do you see oil moving on the top of the breather next to the low oil cut off switch? You can view this easily without a flashlight. Four 1/4-28x3/4 bolts should be 100% replaced going to the breather and I will tell you not to put the triangular foam element back in there when you replace that gasket. That area's probably hemorrhaging the most amount of oil.
New head gaskets, lifters while you have it apart (a small rare earth magnet on a socket extension wiggled just right will pull them free) and knocking the carbon build up off the valves won't hurt and anything on the cylinder before reassembly.
If you have oil leaking straight down from under the flywheel area, that's the front crank seal and 10 mins to replace with a flywheel puller. Put a plain business card between the coils packs and flywheel upon reassembly for proper gap.
After you finish the above burn 20W50 motorcycle racing oil with zinc in the motor and install a fan in the van exhausting hot air out. On top of the recovery tank blowing over the top of the motor is my first choice, something similar next.
Like I said I assumed a lot from experience, but don't hesitate to straighten me out.