Hi Bill,
I used bracket from the Caldillac CTS-V (Alternator & A/C). They mount low and close to the engine.
There is a parts store on e-bay that specializes in Corvette parts for GTM use.
http://www.ebay.com/itm/Factory-Five...FXsd7x&vxp=mtr
Click the link and then click on the "store" to get a complete list of parts that he sells. It may also be an avenue to send a message to request specific parts.
http://stores.ebay.com/FParts?_trksid=p2047675.l2563
They can more than likely be a source for the steering column harness as well. It's worth a try anyway.
Take care,
Mike