I have a 78 440 out of a motor home in my pickup. I had the same problem. There are 3 grooves in my harmonic balancer, thought I marked the right one. Couldn't get the damn thing to run. Finally pulled number one spark plug, brought it up on compression stroke and low and behold, I marked the wrong groove. Checked the distributor and it was way off. Set the distributor so the rotor was pointing at number one and it fired right off. It's the simple things that screw most of us up.