Bench Seat track disassembly...?

[trapdoor2]

Hi gang,

The '69 has the bench seat adjuster arm broken off and Miz Diane would prefer to not have a pair of vice grips sliding around under the seats.

I found a set of tracks for $50 and am in the process of cleaning them up. Of course, now that I have them, I discovered that they're year specific (did a search here...after the fact of course). The driver's side is off of a '72 and the passenger side is off of a '69...figures. However, all I really need is the arm and it is pretty simple to drill out the rivet, replace with a bolt, etc.

What I would like to know is: how do you get the two sliding halves of the mechanism apart?

There is an internal stop both directions...but I can't see past the crud inside to tell how to get the top half off of the bottom so I can clean out the tracks, etc.