New as in new truck?
Then go to any dealer and order the wheelbase and equipment that would work. I think maybe 280" would be minimal.
New as in new to you but used?
Then yep search around for a class 8 that has a long wheelbase, there out there. The alternative is to put it into a good shop and have the frame stretched and stick a box on it.
Will the cost in fuel economy offset the cost of being able to haul heavier?
Yes and no.
First a lot of properly setup class 8s will get better mileage than class 7s.
I know of one truck that is getting 12-14 hauling around average loads but that truck can haul some serious weight. It is a class 8 but carefully setup for mileage. I can reach 11.5 in mine but that's really doing some careful driving.
Many here will say yep the truck with the capacity of hauling heavy weight is the way to go without hesitation but the truth is that unless your company is willing to put heavy stuff on your truck, meaning actively looking to use the capacity, then it may not be worth it.
Is there a high demand for the heavier hauling units?
Again it depends, a lot of companies will say "YEP We need you" but fail to produce the actual work to make it worth while.
I do pretty good with my c unit but know if I was going to go any way I could I would look for a cab over or a truck with a 112 CCB with a 64" sleeper <GASP!> and stick the biggest box I can on the truck.
Again the question of lift gates is a pretty cut and dry one for the same reason, will the company use that lift gate at least four times a month to make the ROI worth the investment - seeing a lot of companies pay only $25 - $50 for the use of the lift gate. The motor and pump on many of them cost more than $350 just in parts to repair (which by the way very few places repair them they just replace them and I know they cost a bit more than $350), so that means that at $25 a throw, you have to use it 14 times to cover the cost of the pump and motor. That doesn't include the cost of hose and fittings to do a field repair or the cylinder seals which are cheap but expensive to R&R.
