When you first push a contact from Crunchbase to Salesforce, you will be asked to choose to push as a Lead or a Contact. This selection will automatically become the default for your convenience.
You can always adjust these settings by navigating to your Salesforce integration tile of your Account Settings. (Account -> Account Settings -> Integrations -> Salesforce).
Under Push Settings, you'll see the option to Always Ask Me. Select that bubble, then you’ll be presented with the Lead or Contact options each time you push over a contact.