Does it need to be a toyota rear end? I don't know much about those, except that the one in the tundra looks beefy. There are many rear ends a 500 hp truck with an auto won't seriously threaten if you won't be running a transbrake. Any chrysler 8 3/4, ford 8.8 (might want upgraded axles for that), dana 60, gm 12 bolt, hell a gm 8 1/2 10 bolt in decent shape should hold up fine if it doesn't have the infamous gov-lock out of a truck. A 9" ford will hold up fine if you won't be launching real hard. If you will and you want to use a 9", try to find one with a nodular chunk. Those tend to blow the pinion support out of the housing during launch much less often than the more common ordinary cast iron chunks. Will you be running leaf springs? Can you weld, or get someone to weld spring perches on an axle if needed? If so, then pretty much the only things you really need to worry about besides strength are matching the bolt pattern to the front of the truck and the overall width of the axle.