WHILE EN ROUTE, THE L ENG SUDDENLY LOST POWER & WOULD NOT RESTART, SO THE PLT FEATHERED THE L PROP. AFTER LETTING IT COOL APRX 5 MIN, HE TRIED RESTARTING IT AGAIN, BUT STILL WAS UNABLE. HE STATED HE THOUGHT HE THEN SECURED (FEATHERED) THE L ENG. THE PLT DIVERTED TOWARD INDIANAPOLIS. HE NOTED THAT THE R ENG BEGAN TO OVERHEAT & LOSE POWER. SUBSEQUENTLY, THE ACFT CRASH LANDED IN A CORN FLD AT NGT WITH THE LNDG GEAR RETRACTED & W/O LNDG LGTS (LGTS WOULD NOT EXTEND). AN EXAMREVEALED FUEL WAS REMAINING IN ALL TANKS. SHERIFF PSNL HAD MOVED THE FUEL SELECTORS WHEN THEY ARRIVED, SO THE SELECTOR POSITIONS WERE NOT VERIFIED. FOUND L THROTTLE FULL FWD, L MIX CTL MID-RANGE, L PROP CTL FULL LOW RPM (NOT FEATHERED). THE L PROP WAS NOT FEATHERED; BUT THE R PROP WAS FEATHERED (PLT SAID HE FEATHERED IT JUST BEFORE IMPACT). A TEARDOWN OF THE L ENG REVEALED THE #4 MAIN BEARING HAD FAILED; BOTTOM HALF OF OIL COOLER WAS 95% BLOCKED FROM SOFT METAL CONTAMIN- ATION, PROP GOV MOUNTING GASKET WAS 75% BLOCKED BY METAL CONTAMINATION; BUT THE L ENG CRANKSHAFT WOULD STILL TURN.