Can I deduct FMV for a car donated to a charitable organization that uses the vehicle and how to do so on tax forms (i.e. church camp that does not sell)?

I donated a vehicle to a church camp facility.  They provided a letter to me with the detail of the vehicle I donated.  The letter states they will use the vehicle and will not sell it.  

I am completing the charitable donation in Turbo Tax and it is asking for a 1098-C or written statement.  

I don't know if this letter is acceptable to IRS since it does not state the value; I have the value from NADA, which is higher than the $500 value.  

If I do not have information about the Gross Proceeds (as if the charitable org would provide upon sale of vehicle).  Should I use my value as the Gross Proceeds to take the full value of the donated vehicle?

Or is the donated vehicle full FMV disallowed for a situation like this?