Well, as you probably know, the early Mustangs use the same chassie components as the Falcons, except a few small peices. There may be a kit to change it, with templates for spreading the shock towers which needs to be done, there just too close without it done. Also, what Big block, FE big blocks or 429/460 BBF's? More than likely, there is only a kit for the 429/460. I have seen MII front x members grafted to the old unibody's so the old front can be removed, allowing all clearences needed as the MII dose not have 2 giant shock towers in the engine compartment. My oppinion, get a 260/289/302 and drop in, much easier and with a built up engine, you can make a nice stout motor.