comp 262 vs 268

They are pretty similar so it's more of a case of which will work better with what you're not changing. The 262 is slightly shorter duration and lift, which will tend to idle cleaner with more vacuum, and start making power earlier regardless of the pistons or static compression. If you have stock parts, you have a lower static than the books suggest and the 262 will be "more forgiving" than the 268. Teh 268 will make more power, obviously bigger means more power. But the drivability may be compromised where the 262 will be almost as strong, but more drivable in a stock longblock.