As you probably know, going above with plug wires and rams horn manifolds means the wires will get cooked where they lay on the exhaust. Best to keep them underneath as you planned, and use some brackets to drop down from the lower valve cover bolts.
You could get something like the Mr Gasket wire loom adapters #9870, and then instead of using the small 90 degree brackets to mount them above, make small aluminum sheetmetal brackets to locate them below the rams horn exhaust. Or just make the sheetmetal brackets to drop off the valve covers and tie the plug wires to a hole in the fabbed bracket. The aluminum sheet is easy to bend and cut into strips, and gives a nice finished looking support.