From what I have read on TBN, your
L3400 is not too small for a
grapple , whether it is a bucket
grapple or stand alone version. WR Long makes a
grapple (OBG2-48) that will work on a B series Kubota. Just don't go buy a
grapple that is sized too large for your tractor. The other option is a bucket
grapple. It uses your existing bucket with a
grapple arm bolted to the top of the bucket. With either option you will need a third function valve to control the
grapple arm.
There are quite a few threads on TBN that are dedicated to grapples.
Jim from NH