I just discovered that the Quarter Inching Valve setup from newer B7510's will install on B7500's. (Well at least the last production run of the B7500's)

First thing to do is look at a B7510 right fender at what is called Assy. guide Lever RH in the parts book. (Which is the plastic part on top of the fender). Lookk how the 1/4 inching assembly is mounted on the plastic part of the fender. Look at the recessed plastic where the bolts slide to adjust the 1/4 inching.
Now the thing to do is remember exactly what it looks like and then go to your Older B7500 and see if it is identical.
If it is you are in luck! Here are the part #'s from kubota to instal the assembly on your B7500:
Quantity-1----6C190-52140----HOLDER HYD. LEVER UP
Quantity-1----6C190-52160----HOLDER HYD. LEVER DO.
Quantity-2----31351-18790----BOLT FLANGE
Quantity-2----31351-18860----WASHER

Just install the parts the way they are installed on the B7510, adjust and enjoy.

The reason I knew it would not only install on my B7500 but also work is I was looking at the newer B7510 and I asked to try it. I noticed that the whole valve assembly works the same as my B7500.
Install time is under 3 minutes and aprox. another 5 minutes to adjust.

Price was just over $30.00 for the parts.