5th wheel conversions

[04mustang]

Hi,
My city, for whom I work, has a m1088a1 with a 2" sliding Holland 5th wheel.
We are needing a 3.5" 5th wheel to tow a WD6S 6000 gallon water tanker.
Ive located a Holland 3.5" sliding 5th wheel from a frieghtliner m916a1. The slider rails look identical and they are both for 34" frame widths. My question is, if anyone knows, will I be able to slide the old smaller 5th wheel from the m1088a1 and slide in the larger 5th wheel without any modification?

The tan setup in the photos is of a m1088a1. The green one is the hitch ive located for sale from a m916a1.

Thank you,
corey

 

[fasttruck]

Have you thought of just switching the lower fifth wheels and leave slider in place? that might work if the trunion pins are the the same size.