Plug Wire Routing w/ Fab'd Valve Covers

I think it was Moroso that sold some chromed ones that were basically a mounting point bracket with little 'branches' with four grommetted holes in them. They fit under a valve cover bolt. Kinda cheesy but they might work. I'm not seeing the ones I pictured in my head on Google search results but something like this might work for you that doesn't involve the valve covers. spark plug wire loom chrome moroso - Bing
You can also do a custom job using zip ties.