Not having a forklift or a transmission jack handy, I wondered how I was going to maneuver the old pin box extension out and the new GlideRite pin box extension in, then I had one of those duhhhh
moments. I used some adjustable sawhorses with a couple of sheets of 3/4" plywood across them, some 4"x4", 2"x6" cribbing, etc. to support and locate the pin box extenions. Then I used the front jacks of the 5th wheel to lift the pin box off the original pin box extension, swapped it out on the plywood for the GlideRite, used the cribbing to get the GlideRite situated and then, again using the front jacks of the 5th wheel, lowered the pin box over the GlideRite pin box extension. It worked just fine, as does the GlideRite.
Rusty