If the car originally came with a hi-po 289 there should already be correct wires in the under dash harness.
If it has never been wired for a rally-pac then Natioanl Parts Depot (NPD) has a kit for $24.95 with the harness extension you need. Part # is 10B943-1A.
www.npdlink.com
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"yeah though I walk through the valley of the shadow of rice, I will fear no turbo for torque art with me. Thy rods and thy crankshaft, they comfort me."
1965 Fastback 289 hi-po 3sp.
1973 coupe 302 4V auto. -SOLD
1994 GT 'Vert