180 degree headers are for V8's where they have unequal firing pulses on each bank (when looking at each bank separately). They allow you to intermix the primaries between the banks to end up with 2 collectors with equally timed pulses that are 90 degrees out of phase with each other.
The 60 degree V6 already has equal firing pulses on each bank, so all you need to do is make equal length headers. Once done, there would be 120 degree phase shift between the pulses at the collectors, but perfect uniformity in the timing of all exhaust pulses.
[This message has been edited by fieroguru (edited 07-14-2013).]