After sliding the stall converter on the 902 tansmission spline should it be able to turn freely?

Should turn pretty freely. You will likely have to support the center of the converter as you spin it (like the engine would).

Make sure that it drops in far enough. There should be 2 distinct detents or drops before it is seated deep enough. the face of the converter will be 3/4 of an inch back from the leading edge of the belhousing. If it isn't in deep enough it will bind on installation and not be seated into the front pump. DO NOT continue installing if this is the case. The converter should have to be pulled forward to mate up to the flex plate. There is only one position that it will bolt to the plate.
902 transmission??????