i am trying to switch all of my gauges over to autometer sportcomp. i am using the mechanical speedo. my question is which speedo cable to use. i have done a search and read a lot of good tech articles. i read an article by mike ervin on 73-87.com and he said he used Napa PN 6151603 for his 85c10. i talked to the napa guys and they said that cable is for a J10 and is only 50 inches long. i also got the PN for an 86 K5 and it says 100 inches long. i know the gm cable wont work because it is clip on and the one i need is thread on. if there wasn't so much of a difference in size i wouldn't think twice, but a fifty inch difference makes me a little unsure. does anyone have any other part numbers I should be lookin at? thanks and sorry so long.