I am using a lot of HTTP Requests in an application that I am writing which uses OAuth. Currently, I am sending my GET and POST requests the same way:
HttpCo
You need to set the content type header if it's required by the addressed HTTP server. There's really no way for us to know if it is or not.
The content length header should be calculated and set automatically if you don't set it explicitly, but since you know it beforehand anyway, I would set it so that your content is not unnecessarily buffered by the HttpConnection before actually sending the data.