I'm 99% sure the LWB tank won't fit between the chassis rails, which is part of the reason this one was mounted like this:
I'd say the centreline flange of the tank would have to above the rail, which is going to put the tank a long way into the passenger compartment.
Great for clearance, but pretty limiting and annoying for carrying anything.
The SWB tanks fit without a problem.
Regardless, all mounts have to change. It's quite a big job.
Steve.