DRG CLB AFTER TKOF, L ENG SEIZED. PLT SAID HE ATMTD 1 ENG RESTART; PROP WOULD NOT ROTATE OR FEATHER. NO EMERG DECLARED. PLT STATED ENG SHUT-DWN PROC WAS USED, SCIENTIFIC BUS SWS WERE SHUT OFF, R GEN WAS RECYCLED & APPEARED TO OPER NORMALLY.PLTS GOT IMT VECTOR TO RTRN TO MARTIN (MTN) ARPT, BUT RADAR CTC WAS LOST FOR ATB 5 MIN. ELEC PRBLMS WERE ENCTRD & PLTS HAD PROBM MAINTG HDGS, THUS WERE DELAYED IN DIVERTING TO ALTN. WITH L PROP UNFEATHERED, THEY COULD NOT MAINT ALT. DUE TOBAD WX AT MTN, THEY DIVERTED TO BWI. RADAR & RDO CTC WERE LOST & THEY COULD NOT RCH BWI. DRG FORCED LNDG, ACFT HIT TREE & CRASHED SHORT OF INTENDED LNDG AREA. TEARDOWN OF L ENG REVEALED #4 & #5 CON RODS HAD FAILED AT CRANKSHAFT; THEY WERE DISCOLORED FM HEAT & SCORED; OTR ROD BRGS HAD INDCNS OF OIL STARVATION. METALLIC DEBRIS FM FAILED ENG FND IN OIL SYS. SVRL OIL FEED HOLES TO ROD BRGS WERE OBSTRUCTED WITH METALLIC DEBRIS. FIRE DMGD MOST OF THE ELEC SYS. ACFT (MODIFIED FORENVIRONMENTAL TESTING) NOT FLT TESTED FOR DRAG INDUCING MODS; WRITTEN FLT CREW INSTRNS NOT AVAIL FOR MODS.