swapping 68 chevy front clip onto 71 gmc-questions...

[67cst]

hey guys, i found a clip for my gmc and im just wondering about the wiring, since im going from 4 headlights to 2 whats going to happen with my wiring? do i need to take the whole wiring harness off the 68 parts truck and swap it on the 71,like the firewall and forward half or....? i just want to have it all worked out so i dont have a bunch of problems during the swap

thanks, DEREK