I need to purchase TWO of the roller assemblies and the track (ONE) that they roll on.

Hello, Rick! This roller looks very close to our 81-158. I think this may be what you want, but I note that the width is a little different than yours. Ours is 11/16" to your 5/8"; that's not too far off so you may want to triple check it just to be sure. The length also differs but it's not an important measurement, so you can safely ignore it.

Alternate image for 81-158

As for the track, we don't sell this exact style. The only patio glass door track we sell  at all is our 80-106. The good news is that I still think it will work; it's fully compatible with the 81-158 roller I mentioned above, and while the design is different it should still fit in your threshold. Look it over and let me know if you had any questions.

Profile diagram of 80-106

We don't have any other door track, unfortunately. As mentioned in my previous response, the 80-106 is the only patio glass door track we sell. I think it will still function, but it will take some handiwork. 

1. Firstly, you'll have to buy two versions of this track and butt them together to make up the 8' length you require. You can cut the excess off with a fine tooth hacksaw.
2. If your original track is raised, then you would need a piece of wood of the same length to raise our track up by the same amount.
3. Lastly, as for our track being skinnier, that won't really matter. It is intentionally designed to be smaller so as to work in a much wider variety of threshold sizes. Due to its narrow design is can be adjusted to whatever position is needed for it to work with the door.

I know that's quite a bit of work, but if you can account for all of that then our 80-106 should work without issue. Otherwise, we have no alternative.