To do a first gear change, you need to change them all. In a regular T5 the ratio's are as follows: 3.35, 1.94, 1.33, 1.0, .68, a world class or Cobra or early T5 has the 2.95 first gear. As for fifth, I think there are about 2 different ratios including .68, .80. I am not really sure what has to be changed with 5th but I would assume 2 gears. For a first gear change it would be everything inside pertaining to gears, main shaft and counter shaft. Hope this helps. Good Luck with it.
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