Using a 305 head on a 350 block with a flat top piston and a mild lift cam isn't an uncommon thing. Many people have done it. The computer shouldnt know anything different because the computer is controlling the fuel injection and im not changing the injectors or the intake so changing the block shouldn't mess with any of that. Also another question, how stout is the 292 inline 6cyl that you find in like UPS trucks and stuff? A friend of mine said he has seen them put into full size trucks and they just haul ass because the 292 has such a long stroke and potential to make tons of torque.