HDsilverado

i everyone. hows it going? Well im having a issue getting my 350 to run. its in a 78 cutlass it has hei ignition. it has new cap and rotor also. the motor has the old 67 camel humps on it, roller rockers. just trying to give as much info as i can. ive got the timing set right im almost possitive but at this point im not sure of anything , this is going on three weeks of trying what i know to try.well when i dropped engine in it tried to fire or sounded like it a couple times but has never fired up. it has spark and fuel. got a couple carbs tried both floats not stuck. Anyway what happens is it just spins and spins if u give it pedal it will puff out of carb and small gas particles come out. if i disconnect the power to distributer it does not do that it just turns like it has no spark, witch it dosent but if i plug back in i can spin and as soon as i give it gas it spits and puffs out of carb. ive tried ajusting timing but same result only time it does not puff is no power going to distributer. if anyone has ever had this happen or may be able to help i would appreitate it more then i can express. thanks ahead of time.