I am looking to start that this fall. I'm going to start with the 94-98. A LOT of people have asked about it. I am going to look into it this fall if all works out I should have it ready by spring.
the only difference i can think of that would be a difference for 99-04 would be the angle of the upper intake.
a 99-04 kit will be in more demand, and most (emphasize most) 94-98 owners will swap to 99-04 heads and intake before buying a Turbo
just some food for thought