89' f150 wont start

   I have a 1989 f150 inline 6, truck has a used ECU and wire harness from same year truck w/dual tanks and
5 speed manual the truck STILL wont start. Is there something else in the cab that would not allow truck to
start and yes iv'e checked the reset switch and its not tripped. I'm getting fuel at the rail but when i hear the
pumps activate i here a gargeling sound in tank is this normal. Also my gas gauge says 3/4 full and its
almost empty. This truck was rear ended and hit right where the ECU unit is and the story told is that it
never ran again. Everything that iv'e done to it is making me believe its something inside the cab and i say
this because i had to replace the frame, the truck i bought was a 91' automatic inline 6 and i drove it home
and kept the running motor on the good frame and got rid of the cab and used my cab now it acts just like
it did before i did the switch. The only change is i went from auto. to stand. but i made the adjustments for
this. My key switch has been very stiff since iv'e owned it and now the truck wont turn over by key
anymore. I'm hoping this is just the solidnoid, haven't found the one from the automatic to see if thats the
problem.