I bought a rear hellwig sway bar for my F 250, diesel, 4x4, 1991. Only the rear sway bar is available. They do not make them for the front with diesel engine. I have the leaf suspension in the front. I hear that it will greatly improve roll stiffness when my camper is on.

Is there any problem installing bar just in the rear?

 

I don't know about the Hellwig specifically but I put air helper springs on only the rear axle of my 91 F350 Diesel SRW and they work great. Handling is terrific compared to how the truck handled before I put them on. Since the camper load is mostly on the rear axle I suspect you'll experience similar results if you only install Hellwigs on the rear axle. It is also my guess that your front leaf spings are identical to the leafs on my F350 4X4. I just took a set off an F250 rear axle and with the exception of the added overload leaf on the F350 they were identical. The axles were also identical.

 

There were a number of posts about this suggesting a rear only stabilizer bar caused or contributed to steering problems. I would be interested to hear your experience as this is exactly what I had thought of trying.