Well, I guess I will add to the confusion....(yours and mine)....
I went to that "other" website to take a look at the parts manuals.
78 Intruder and Invader used aluminum rail part # 39105-3501. Same part # for both sides....meaning there had to be no offset??
79 Intruder and Invader used 2 of part # 39105-3502. I suppose the new # was for the change from the 78's using the threaded eyebolt adjuster for the front spring and the 79's changed to the cam shaped thingie...?? The cam required a couple more holes drilled in the rail for attachment??
 The 80 models get really weird...
 The Invader calls for 2 of rail # 39105-3507  (identical with no offset??)
The Intruder shows using 2 different rails, a left and a right with part suffix -3508 and -3509....had to be offset??
 The 81 Invader doesn't count because it changed to the newer Vari-Ride skid, but the 81 Intruder shows the same 2 rails (offset??) as the 80 model.
  So...I took a look at the track part #'s:
All of the 78 and 79 models came with track # 39125-3502. The original steel bar track that was recalled??
 Someone has hand written in a new track #.....39125-3511 in those 2 parts manuals. I assume this was the replacement track during the recall??
 Again, the 80 models are a bit weird....the Invader calls for track # 39125-3505. The Intruder calls for 39125-3512 (as does the 81 Intruder).
 I dunno.....I think I need another coffee....
 

For some strange reason we have a couple of  suspension skids sitting in the garage right now.  They probably need to go to the machine shed so that we can have more room in the garage.  But that is for another day.  Walking past them today I noticed something that I had never noticed before.  The skid from our 78 Intruder, which came out of our first 80 Intruder that met an untimely demise, has off-set rails.  I don't know how it happened or why, I am sure I have looked at this skid multiple times.  But today I was thinking about whether or not to change the hyfax and all of a sudden it hit me that the rails were not symmetrical.  And do not look like any of the other 79 or 80 skids that we have.  So just when I think I can't get any more confused, something like this jumps out  at me.

That looks like work.

A LOT of work.  I was sore for 2 days.

That looks like work.

 Saw this over on vintagesleds.com just now.
Anyone near North Dakota? Go for it!   
Scroll down the listings.
https://vintagesleds.com/classifieds/