i have a 81 cutlass supreme 2 door brougham witht he 231 in it. The engine is starting to smoke pretty bad and will not run in the cold unles it heats up for like 30 minutes. Now, i have a 307 out of an 84 442 that just needs the heads reconditioned. what i want to know is if the 307 can be used as a drop in replacement for the 231 without changing the rear-end, transmission and the ECU?