mostdef

ok i have an 87 t top which u all may know is speed density...but im recently going to add a f cam some gt 40s and a gt40 upper and lower...from what i have heard the idle gets all ouuta wack in the speed density cars so i gotta convert it...heres my question...i know i can use an 89 harness but am i going to have any problems...i tried to use a 92 harness but it didnt send power to the fuel pump and i wasnt tryin to re wire everything....so sholud i get the whole 89 harness or just use the pig tail they sale and splice into the existing one????