Yes, if you don't buy stock trusses and talk to the truss builder, they can properly scale up the truss to handle the increased ceiling load without issue. I doubt the #60 truss load that you quoted is the ceiling load that will need to be. The 60# is probably the snow load on top of the roof. Most standard trusses only have a 10 or 20# ceiling load, some pole barns have none. You will want a beam to sit on the tops of the bottom chord to spread the load out to multiple trusses.I am working on a additional option for my soon to be built 48x36 pole barn. I will have a mezzanine in part of the building (12x40) and would like to put a unistrut trolley and winch to lift objects into the mezzanine. Is there a type of roof truss that will be usable for this type of situation? (heaviest would probably be #100 since I will have to move it once it gets up there. Current plans show 4/12 pitch with #60 load.