Hi there,
Go buy the ones at GAC.
I have a guideline Le Cie 12ft 6in 8/9 and have a full selection of heads for that. They are fantastic for the rods. The ones at GAC are the distance ones which are 13m long, which are a little more difficult to cast if you are new to Salmon fishing, but should be no issues. I learnt using these heads and they are great. I find that for big tubes etc i prefer the 11.5m short cut ones, as they turn the fly over better.
I have a selection of 9/10 wt ones that i use on my Loop 14ft opti spey, and they go like a rocket. They are my fav shooting head, and with them being prelooped ( the ready to go ones ), they are easy to use, no faffing around cutting down for the rod.
I have a couple of the original guideline shooting heads that you have to cut to size, so that they suit your action, they are good but are a bit more faffing around. You can go to the guideline website and it gives the recommended head wt for the rod, and then you can use the power taper calculator to work out how much to cut them down by. Make sure you measure them first though as mine was supposed to be 13.5m, and it was 13.2m in real life, so didn't need as much cut off.
Let me know if you need any help, as i went through this about 18 months ago when i started salmon fishing also.
Cheers
Mark