Get a shorter final drive
Lighter flywheel
BOOST

But seriously, how hard do you need it to pull in 4th gear? 5th gear is not a racing gear obviously. Not to mention you are at a high altitude, so it's not going to pull as well anyways. And if he has agressive cams, he may want to check with Spoon first to see how much difference in timing you can have between the intake and exhaust cams, because it's possible the valves will hit...this is the case with skunk2 stage 2 cams.