I have all the race mounts. I got exalted 999/1000 on all Horde. At level 70 I went back to the each of the start zones and did any quest I could that I skipped. Example would be Undercity Rep. Goto Tirisfal Glades and do all the quests. Then Silverpine Forest and Hillsbrad Foothills (Tarren Mill). The quests are easy at level 70. Yes they are grey but they still give full rep! I remember a long time ago I did this and was getting 10 rep. per quest. (Like the xp for a grey quest the rep was “nerfed” too) However for a while now it has been changed back. I was getting 150, 250, 350 rep. per quest, as was listed on the quest write up under rewards. (http://www.wowhead.com/)

Other clues are the race of the quest giver. Like in Freewind Post, there is a Blood Elf quest giver, so Silvermoon City rep is what you get. Also not all quests gives fraction rep. I’d look up the quest to make sure. http://www.wowhead.com/

Over all I did it for the mounts. However it looks so awesome on www.wowarmory.com to have 5 blue smiley faces at the top of you Rep tab.