The gas gauge in my 1990 765 turbo is not working. Sometimes it shows inaccurate readings but it is usually completely off. My mechanic did some testing and says he thinks it's the wiring in the dash. He says he needs about 1.5 hours to fiddle with the wiring to get it to work. Would it be cheaper to splice in an aftermarket gas gauge? Which type/brand gauge should I get and where can I find it? Thanks for any help!