Would it be worthwhile putting the E7 heads off my ef onto a mates stock 69 fairlane. If not what about just the springs, rockers etc.

Not sure about the valve springs but I can say with certainy that the rockers won't swap, the ZC uses rockers with rails which locates rockers via the valve stem, bolted on via press in studs, E7 uses bolt on rockers similar looking to the Cleveland and 250 crossflow rockers.

I wouldnt bother with the E7 heads unless ZC heads are RS.