In InitializePageContent in selectaddress.aspx.vb, you'll find this line
Code:
litNewAddressForm.Text = newAddress.InputHTML()
This is the line responsible for the different form elements. InputHTML() is a method in the AspDotNetStorefrontCore project (or the AspDotNetStorefrontCommon project depending on which version you are using) in the Address class (Address.vb). Access to this code requires source, and changes to the Address class will require a recompile in Visual Studio.
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