The flare angle on stainless steel brake lines is the same, most commonly 45 degree double flare, it should be just the same as a normal steel brake line.
If you will be buying prebent lines then buy the ones you need.
Most GM proportioning valves have two separate outlets for the front brakes, so each brake gets it's own line. Then the valve has one outlet for the rear brakes that goes to the flex line at the axle, then splits after that.
I think you will be confused about what brake lines you need until you have all the hardware in hand and installed on the truck, including the MC and proportioning valve. Then you will see where the lines need to go to and from. Unless you are real careful and have a factory setup prebent lines may be a mistake, at least make sure you can return them if they won't work.
Grigg
