I came up with a S10x25.4 or larger.  I limited the allowable deflection to 1/4" and the beam size is governed by deflection requirements, not stress.  Regardless, I checked if for a 2g impact on your won ton load and it's O.K. for that.  Also, I chose the S shape because trolley wheels are usually canted for these beams.  Does this work for you?

Bob G.

Thanks fellas! I think im going with the s10.