i would contact Speertech or John Leonard at modern vintage. they both build harnesses and could probably help with your project. are you wanting to use stock gm gauges or aftermarket? if using a Dakota digital gauge set up you can use a bim module to get the data.
http://www.speartech.com/
http://modernvintagesystems.blogspot.com/
http://www.dakotadigital.com/index.c...rod/prd752.htm