I'd start with aluminum--easy to get, easy to replace, and a wide range of spines and weights. I'd try for an arrow weight (finished) of 368-460 grains or more. Heavier arrows will drop a little quicker, but they are quieter, easier on your bow, and aid in penetration.

I don't have enough experience with moose to say if I'd be comfortable hunting them with 46# (hunted them once, no luck). I've heard of it being done consistently with 50# recurves, and saw where a fellow in Australia killed a huge camel with a mid 40's longbow, so I do think it could be done. I'd opt for a close shot, with heavy arrows they fly perfectly. Don't think I'd try it this year though--you need time to get comfortable and accurate before hunting with it.

Good luck!

Chad