ironman.civilwar

how do i find out the timing on a 1988 cheverolet c1500 4.3l v6?the motor i was told was pulled from a 1987 s-10.the distributor came with it.i tdc'ed the motor and have set the #1 plug wire at 6,7,and 5 oclock positions.on 6 it wont fire at all,on 7 it will start but not time up correctly.it idles very roughly and carbons up the plugs.the best i could get was a lopsided lopeing at idle.if i pushed it up on rpms.it would run .but i cant get a smooth idle .on 5 oclock it backfires thru the carb and starts fires.i am desperate and totally frustrated.i have been on this for a week now and changed everything.including the throttle body.i also changed the fuel filter.yes,i also used a timing light.gets the mark close but jumps between the o degree and 8 degree marks.also i was told there isnt any such thing as an 87 4.3l v6