Flex it out and measure how much movement you have. The more vertical you can get them, the better it will handle "on the road" and still have plenty of articulation off road.
The biggest reason for angleing them is to get more travel without running out of shock. At an angle they don't extend and retract as much. The down fall is, when you go around a corner, if both shocks are mounted close togeather at the top, the truck pivots on that spot and the shocks don't really have a chance to do their job. So you get more lean around corners.
If you have enough travel with them vertical, then you'll be good off road and still stable on road.
Also remember to mount your shock eyes so the hole is facing forward and back with the truck. That way when the axle articulates, the shock will pivot on the bolt. If you mount the hole cross ways, the bushing in the shock has to do all the flexing. Which will cause a bind, and you'll lose articulation.
Good luck
