5.3 swap done on a 70 feels rough

[camaney]

I finished the engine swap from 03 pickup on my 70 and im having a terrible mpgs . Before The swap I change the knock sensors and everything that need it to change new but the injectors.. The truck idles good , runs good at times, no noise or knocks but there is times that it feels like missfire lack of power or tranny kinda hard to shift, i got the check engine light with 4 codes fist it n/a (i guess not avalable) po332 po327 and po332 again(knock sensors)its a new haness from painless ,auto trans.. Any idea what could it be? Should I get new sensors? Engine has 80k miles supposedly thanks for any input