will it be that hard or is it possible to change the c3i and ecm? the common parts list does not seem correct.it has the same part # for 84/85 as 86/87,coil,ignition module.
Converting from an '84/85 ECM to an '86/87 ECM is a great article on how to do this. The earlier and later ECMs are NOT the same (as you pointed out)