How will my truck handle these two 5th wheels?

My thinking has always been, if you need a diesel to pull it, you are going to need the higher capacity 350/3500, to carry it.

A 250 could be modified to carry a similar load, as the 350, but may cost more than just getting the 350 to start with.

Your yellow tire placard will give the manufacturers payload number. It will be on the driver's door jam.

Jerry