I did this with Famine, Catch and Tough Luck on Heroic. Famine doesn't effect ammo crates, catch means you are shot less as you are more often grenaded which are easier to avoid and tough luck just gives the point boost since all it does it makes enemies avoid you more.
While playing you should aim to kill most of the enemies until you get to around 30k to 35k, and then you should simply try to avoid most enemies and finish areas as fast as you can because once you go over par time your score will begin to decrease, if you are using the competitive scoring to see the score.
The normal scoring does not seem to work for all levels but it may work on this one for you. If it doesn't but you don't mind not keeping track of your score as you play then it may be worthwhile to use this one as it does not start decreasing your score after a point.
Other than that you should be fine, I finished with 37486 and was 10 minutes over par and was around the second pillion when it began to decrease,
although this also had the time multiplier added on afterwards which boosted it slightly.(I think the competive score uses the time bonus anyway, which is why it begins to go down after a while) It was still around 34k when I finished the actual mission.
Good luck, this seems to be the hardest one of the par score of all the Halo 4 levels to accomplish.
EDIT: The par score for this level was altered with a title update that hit around Christmas, it is now 22,000 and as such is now easier to accomplish with a skull or two less.