Well have no experiance with your situation but as far as the header wrap goes, check with thermo-tec. they have sleeves that are designed for keeping wires and such from melting. The header wrap per-se is just to keep the heat in not to reflect the heat. The sleeve stuff they have i think is in the 1300ºF range. But Yes i agree that the cable should NOT be touching the tube at all.
Good luck

http://www.thermotec.com/products/full/full.html
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71 Pinto Sedan
5.0 block,B303,1.7 Rockers,beehives,'68 ported heads,Coated custom Must II headers,Edlb Airgap,Holley570,Msd Billet,Crane HI 6,Milodon 8 quart Deep Pan,2.5" 40 Flowmasters.

<font size=-1>[ This Message was edited by: 71hotrodpinto on 10/23/06 6:27am ]</font>