88 bronco 11 won't start

it tries to start but won't. changed starter motor, water pump, fan clutch and radiator. still won't start. was running before i stopped driving it last month. it has an oil leak about 1qt. every 1000 miles or so, but don't know where from and also needs a muffler. what could be my problem? PLEASE HELP ME :banghead:

update:
got new battery and found out the alternator blades had chopped up the negative cable. so i replaced the cable. and checked the wires found out wasn't getting any spark so i replaced those. it tries harder now but it still won't start.