Google and then download the "Copper Tube Handbook". It has a lot of great information on copper pipes including soldering techniques and charts on pressure ratings. I could not find Stay-brite #8 easily when I started my copper airline project. Based on the chart in the handbook on "Pressure-Temperature Ratings of Soldered and Brazed Joints" (table 4a), I chose a 95/5 - Tin/Antimony solder which was readily available locally. It worked very well. I had no issues and no air leaks on first test.
Good luck,
DC