tctim - For the size (8' x 8'), loading (150 PSF), height (3'6"

, and embedment (44" in concrete) that you specified the following combination of treated southern pine members (#2 or better) should be adequate:
1. 2x10 stingers, 16 in. o/c, 8' long (max)
2. Double 2x10 headers, 8' long (max)
3. Four (4) each 4x4 posts, supporting each of the two (2) double 2x10 headers. Posts approximately equally spaced.
4. Suggest that you consider 2x6 or 2x4 decking instead of 1x4.
Also please consider retaining a local structural engineer to detail the connections of the members based on your specific situation. Typically this is more critical for heavy loading applications, such as yours, than sizing the members themselves.