engine swap 78 chevy 350 into a 89 chevy c1500 looking to convert to fuel injection??

[82chevy350]

i do know that my 1990 silverado that i sold today that if the speedo is not working it wont shift into the last gear because it cant show the trans how fast its goin and it leaves the last shift point out

 

[rocknturtle]

I have this problem and I would really appreciate some help. I have a 92 silverado stepside 4x4 it had a 305 that blew up. I put a 78 350 in it and used the fuel injection and intake off of the 305. It runs but it acts like the timing isn't advancing . It has headers with on oxygen sensor I read this thread and was hoping someone could help me with some ideas for straighting it out. I know nothing about comp,or Tbi or whatever. It was my grandpaws truck and I would love to get it running right. thanks for any help.