Fifth wheel height.

Curious - you need the added height for weight distribution, or just for dumping or unloading?

If just for unloading I would think that installing a valve to over-inflate your tractor air bags might work.

 

these are 1/4” wall, 6” wide x 2” high. 54” long with 4” bolt spacing

 

If the OP doesn't want them I might. A couple more inches under my lowboy neck for clearance would be handy. What part of the world are they in?

 

Middle part of Michigan

 

Dang, I can probably have a set made for the shipping alone. We'll see if the OP wants them.

 

When I ran bulk liquid we would just used the tubing like pictured. We did not go to a fab shop. We just bought the steel and drilled it ourselves. That’s the cheapest route. I changed the saddle on one or two. To answer @Oxbow we did it to roll the liquid back to help take weight off the drives.

 

Most tankwagons are 42' - 45' long and even double conical [both ends pitched to a central sump] needs the correct fifth wheel height to scale maximum loads.

OP can get taller mounting for some fifth wheels, some look like the picture above some are just taller blocks for each side, depends on maker and style.

Provost ordered a set of new DOT 407 wagons with a deep pin setting thinking of our 'local' day cabs and all the large car owner operators couldn't scale them until I authorized one to get the pin moved up and move the spacer to the rear.

Corporate maintenance blew a gasket when they saw it in Montreal until I had a talk with the person who specified the original setting describing the size tractors doing the line haul work and he gave the blessing to move all of them.

Never understood his thinking as the Canadian line haul tractors were sleepers too!