Are the beams in one span or are they spliced over the posts. J.

Yes they are splice over the post.

You can span 16' using a triple 2x10'' with no problem. It might be a little tricky holding up the project while your doing that but Im sure you can rig up some temp support including some diagonal bracing.

If you have room for the trailer/truck it would be possible to install another beam under the two existing. This would be a lot easier. J.

Thanks John,

What I want to try is to temporarly support all three beams then cut off the top of the two remaining posts the height of the new beam so I can use the existing post and footings.

That would do it Dog. J.