Best 95 or 96 tandem axle truck for fuel mileage ??

Here in CA a 94 or 95 motor is exempt for a particulate filter till 2016 so I am looking for a 95 or 96 tandem axle truck with preferably a sleeper
Which truck of that year would get best fuel mileage and what kind of mileage can I expect to get. I have an 06 9400i right now that averages 7.5 mpg which will need a DPF come 2014 but from what in have been reading on here international computer systems are not very compatible with the DPF's and cause a lot of down time. That said I need to weigh the cost of fuel for a 95 or 96 truck vs cost of newer truck and fuel mileage with DPF and selling my 06 out of state come 2014.

TIA