A lot depends on what you want out of the car...pure performance, streetability, etc. What is the rpm band you want the best power from? Different header designs produce best power at specific rpm ranges.
Tri-Y headers are best at low end torque production. Long tube headers give best performance at mid- to upper-range rpm's. Block hugger headers kind of split the difference and make for good all-around performance. Tri-Y and in particular, long tube headers can create clearance problems under the hood and with the ground. Tube diameter makes a difference as well.
You need to determine the answer to those before anyone can give you a good answer. I'm partial to Sanderson headers...you can contact them and ask a tech for advice. The same goes for other brands as well.
My own recommendation...regardless of which style you go with...is to get coated headers...Jet Hot, ceramic coated, etc. The extra expense up front pays for itself in the long run...appearance, lack of rust and longevity.
