I used the 93-97 core support, because I didn't feel like messing with the radiator, condenser shrouds, and body mounts.
All I did was remove about a 3/8"x 2" flang from the fender by the core support (right infront of the top fender bolts) because the older core support is just a tiny bit either too long, or too tall, compared to the 98+ trucks.
Then for the hood latch, it had to be moved to the left about an inch, and up about 1/4". All I did was use a piece of thick sheet metal, and bolt it to the old holes, then use 2 J-clips to bolt the new latch to it. (I used a latch from a 98, I'm not sure if they changed after that)
As for the header, I just modified the exhisting mounting brackets.
I also had to take a sledge hammer, and hit the coresupport at the edge of the headlight access hole to make room for the new headlight location.
I should have taken more pictures of the swap... Maybe I'll do that and post a thread. It really wasn't very difficult of a swap.