I have been looking at these. Dual purpose valve cover hold downs and wire looms....
http://www.jegs.com/i/Proform/778/66292BKC/10002/-1
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I have these and they work. They add just a little extra pressure to the valve covers at a point a bit wider than most of the spreaders. The very ends are always a problem on 4-bolt SBC valve covers.
The spark plug wires need to be routed a little unlike you would expect, though. The wires on the left side, from the outside in of the four-wire loom clip, are 5-7-3-1, and not 7-5-3-1, so that the wires loop to the plugs without touching the headers. Same on right side: 6-8-4-2.
I think you can see in the pictures how the 5 and 6 wires come off first and loop forward, while the 7 and 8 wires come off next and loop back. Doing it 7-5-3-1- and 8-6-4-2 makes it impossible to dress the wires so they don't touch the headers.
I got the Proform units above in black on chrome valve covers and they look pretty cool.
As for headers heating the wires, I used Taylor spiral metal wires. You don't need resistor wires if you use resistor plugs. Either-or.
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