HEI is as simple as it gets. do you have spark at the plug itself? you can always pull one and crank it over while touching the base to the block. make sure you're holding the boot and not the metal plug itself or you'll get a nasty shock. do you smell gas/is the carb working? try dribbling a little fuel down the carb to see if it tries to fire a little bit. if you have gas, compression, spark, and air... you'll have a running motor.