We took apart an '88 360 and it also had the rotators and dual pickup dizzy. Don't know exactly what the timing chain looked like- the E58's have more cam to them but I can't say there's a ton more obvious differences between them and their contemporary 360s. The old "HD" 360s (E55 in cars, not sure if offered in trucks/vans) seemed to also have the big cam even if they had the 2bbl. As you mentioned, there were different head cast numbers and they were rated as having lower CR than the "regular" 360s but had more HP and TQ.