CARBURATOR

I have a 64 corvair. The one of the carburators are going bad. Is it possible to throw on 2 4bbl carbs or is this going to take some modifications. I don't know much about carburators, so any advice will help. I am trying to atemp to restore the car for my dad. 

You would need to change the intake

would I have to drill any holes for the new carbs or will it bolt up? and the intake do you mean the manifold or the intake cleaner?

Check these.  I bet at least one will have what you need.
http://www.nationalcarburetors.com/
http://www.thecarburetorshop.com/
http://www.customrebuiltcarbs.com/index.shtml