I really don't want to be offending but you should know about more about Lambos and especially Miura's than just plan to buy one.
A wrong buy can become a nightmare, they are beautiful cars but like beautiful women they need a lot of attention.
I can remember that a good restoration at Bobileff for example costs $200k,
depending on the state of a car the price of an SV can be around $400K.
If you really want to spend that much money for an oldtimer car is a question you have to ask yourself and be sure before you sign a contract.
If you don't know cars by heart take somebody with you who knows them, for example Bobileff to check the car. Of course he will bill you for this, but in the end this will cost you much less than buying the wrong one.
There are many things to consider when buying one, so one of the best things you can do is to educate yourself on the variations. As a general rule, higher serial # cars command more money, but so much of the price is linked to condition.