305/350 combo Help

Ok I have a fine mess going on was wondering if someone could help with. My 91 suburban with 350 decided to give up the ghost after 211,000, no major thing, so in the mean time while I am gathering goodies for the rebuild I dad let me borrow his 79 305. Well after much work and learning many new things the 305 now has my 350 TBI intake and setup on it. Only major headaches where the center for intake holes into the heads due to change in bolt angle and different flexplate (68 Impala) to make the older 2 piece rear main seal motor bolt up to the factory 4L80E. Other than calming down oil leaks in a motor that sat for 6yrs. everything was cool till this am. Now she's blowing major black smoke and loading up to the point that it's sputtering. My guess is that I need to drop my injectors to 305 TBI injectors to reduce flow rate. I know the black smoke is over fueling and it's symptom-matic of an old carburetor that I had with a stuck float. Any opinions on this? I'm hoping i'm just shooting so much fuel that I'm washing the cylinder walls down.
Thanks for any ideas or input!!!!!

Off the top of my head, I'm thinking you might have to change your PROM if you go with the different injectors.