I replaced the Henschen axles on a 2002 Classic with Dexters. I got some additional clearance, but not as much as I wanted so I lifted the trailer using the Dexter lift kit. The mounting holes in the frame for the Henschens were slightly different than the holes in the new Dexter replacements and the lift kit. This is not a big problem. We slotted the rear mounting holes in the axles and later the lift kit about 1/8" or so and they dropped right in. As long as you slot the same hole (front or back) the alignment will not be affected because the frame has clearance holes, not slots.
You might want to consider replacing the axles, as old as they are. Mine had lost about half of their movement range due to sitting still most of their lives. Look at the swing arm the wheel is mounted on. Under full load it should be roughly horizontal. If the wheel center is higher than the pivot point, either the axle is overloaded or the rubber has taken a set. Measure the distance from the wheel well molding to the edge of the rim at the top. Jack the trailer up until the wheel is off the ground and measure it again. It should drop about 2.3" from where it was under load.
“You cannot reason someone out of a position they have not been reasoned into"
Al, K5TAN and Missy, N4RGO WBCCI 1322
2002 Classic 30 Slideout -S/OS #004
2013 Dodge 2500 Laramie 4x4 Megacab Cummins