4x4 span load for 600# bell

We obtained a 4-600# old church bell and have constructed a small bell tower from which to hang it. The top portion is essentially 4'x4' outside dimensions and is well sized to carry the load, now I need to put a crossmember from which to hang the bell. As such, it will only have a free span of about 3'5" and will be bearing 3 1/2" on either end. The bell will hang from the center.

I assume that a treated 4x4 would probably handle that fine, but would probably double it. We don't want to hang our giant paperweight until I find some span calculations to ensure it is quite safe. Where or what are the calculations for such? I know how to find tables to tell me lumber sizes for all kinds of typical building scenarios, but have no idea how to find the capacity for a single heavy object, and I thought someone here might be able to help.