Charlie---
I just completed this very job on my car last week.
Those horseshoe pieces are a pain. The ones supplied by moss are a bit different than the ones in the service book. They install in a different order.
Here's what I got to fit:
Slide the one with the bent fingertips in first, from rear of car toward the front. Bent tips inward toward the differential, not the tire. Then slide the other one from the front of the car back over the first one all the way until the bent fingers of the first one spring up into the little slots on the end of this second horseshoe. This make sure it will not come off. Not even when you want it off at your next brake overhaul!
It's a good idea to lightly lube all these parts that slide together. Even the part of the aluminum cylinder that slides on the brake back plate.
Also, be sure to put the dust boot over the brake line before attaching the brake line. Secure this brake line before installing the horseshoes. This will give you more wiggle room to align the fitting into the brake cylinder.
The hand brake lever goes on AFTER the horseshoes. Yes, you have to fit it though the slot and use a hammer to tap into place. Doesn't sound right but this is according to the service book. It works. If you try to put it on before the horseshoes, the rear horseshoe won't fit.
Lastly, pull the new dustboots over the cylinder and tuck the large loop around the stacked horseshoes. The inside edge of the loop is beveled to fit nicely under the edge of the horseshoes.
Access seemed best on my back from under the center of the car when up on high jacks. (be careful you have the car secure on the jacks. I don't trust jacks). Working from the side and reaching around the brake backing plate is not as easy.
If none of this makes sense, my apologies. It's all fresh in my mind, so I am trying to be a bit helpful.
All the best,
Brian