try taking the positive battery terminal off and let it set for 5 minutes, then re-install. sometimes the check engine system needs a re-boot to clear all the codes that cause it to come on.
if it still is giving you problems, get the codes manually, or go to a place like auto zone and have them hook a diagnostic hand held to it. after you get the codes out of it, it should reset.
As far as the AMC 360....great motor. Just next to impossible to get it to pass any kinds of emissions. And you would be looking at fuel mileage in the low to mid teens at the best.