Welcome Patrick! That's quite a collection of..... um.... parts you got there! A 78 wouldn't have used an 283, a heavy car like the impala was in 78, didn't that one have a 350? I don't think the 283 will have the torque from off idle like the 350 would've. Do you know what it has for a camshaft?

There's a lot of guys here that know the chebbies better than I, they'll be along with more info / questions / answers.. Again, Welcome Aboard!