With 2 inch pipe you will be fine. I was worried about the crossover pipe myself melting the center links, but I wrapped that section and have had no problems. If you are doing the fab work yourself there are 4 things I want to pass on:
1. Use as much of the existing header as you can. It will save you time in the long run.
2. Start with the rear 3 cylinder header tubes. Keep it as close to the block as you can to ensure that you have enough room for the front three cylinders exhaust pipe to clear, but also ensure you have enough room to access the drain nut for the block, and can access your dipstick.
3. Use only tack welds when you are fabbing up the pipes. Only weld the pipes completely when you are absolutely positive of clearances and routing. I was constantly putting the header back on the head to ensure I had the correct clearances. Also on the final welding, just weld small portions of pipe at a time to ensure nothing moves/warps on you due to the heat. If you find a pipe did move a little you can "finesse" it back with a rubber mallet.
4. After final welding, cap the end of the exhaust tube at each collector. One at a time pour water into each tube to check for any leaks. If any are found mark the spot, and then let header drain and dry overnight. Then weld the leak(s), and repeat the test.
