Don't you know that a shark will outgrow a 75g tank in a matter of a year? They grow to 3ft+?? Are you going to upgrade to at least a 240 next year?
I don't think the shark is a good idea. I personally don't think it is ok to keep one in a 75g tank, even if he is a baby right now, he will get much bigger.
But, do as you wish, it's a free world.