I have heard of people gaining like 20-40HP from a manual swap. Is this true or just what they feel? I am thinking of doing a 5 or 6 speed swap but I have no $ at the time. I looked into it and the t45 t56 t6 and the m5r2 are the only manuals that can be used on a 4.6? And the last question is it I were to get a junkyard trans out of a mustaang would it need to be rebuilt? My power goal is 300 rwhp.