AU and ELII cams will not fit Evilchief, you'll destroy your rocker gear if you try as the lifts etc are all different - too big. You could use it if you had the AU rocker gear though AFAIK
EF XR rocker gear is the same as the stock rockers, the springs and cam grind are different though. If I was you I'd rebuild my existing lifters, the kit is apparently about $12 to do the whole lot from Repco, there's a thread on here somewhere which gives the part number.
3.45 LSD - depends who your mates are, I can get one for $500 but most people would expect to pay $800-$1000, so not cheap. Another way to do it would be to get an old 2.77 LSD or something from an EA Ghia and recentre it, my brother was looking at this and the recentre job was going to be $500. 2.77 diffs aren't worth a whole heap, maybe $100 or so, so is a bit of a saving :)
Look, the EF XR cam would give you a noticeable difference over the stock EF cam, depends which way you want to go really. Personally I'm a bit leery of camming a stock head as it won't use the full potential of the cam. You can do it, and you will get a gain, but I recommend you port the head first. Even if you don't cam it at all you'll still notice a huge improvement; particularly past 4500 where the power *used* to peak