Slipping trans?

Alright I have a automatic a904 trans bolted to a 318 small block. The trouble I'm having is that whenever I come to a complete stop at a stoplight or stop sign and press the gas pedal sometimes the engine will rev up then kick into gear. Now does this mean that my trans is slipping or could it be that the kickdown linkage needs to be adjusted.
Any help would be appreciated
Thanks in advanced dom