i have an 81 in my shop right now and im eliminating the ecm alltogether. ill be done with it in a couple days and let you know exactly any problems i might of had. so far ive striped the ecm harness completely out and all the components connected to it as they wont be needed any more. im useing an edelbrock out of the box with a vacuum advance hei and ive also put a non lockup turbo 350 in it rather than wiring a lockup switch. if you keep the ecm im not sure if it will lock up the transmission with a carb and distributor change however its easy and cheap to wire a manual lock up. you can still hook your tach directly to the distributor from the engine harness.