The hose routing is in UPC N40, sheet A6, bottom sketch for a V8 (or sheet A10 for big block V8). It runs between the motor mount stand and the engine block, so yes under the motor mount. There's another good site for information called Team Camaro and at www.camaros.net
Here's a link to a discussion with pictures at that site. However, this person shows a third clip fastened to the motor mount stand, which I don't believe was used in 67 model year since it is not seen in the assembly manual: http://www.camaros.net/forums/showthread.php?t=131437&highlight=power+steering+hose+routing
On both websites you can run advanced searches using key words such as "power steering hose routing". On the Team Camaro site you may need to first be in the appropriate section (Brakes, Suspension, Steering) before running an advanced search.
The amount of slack would depend on the hose you are using - if it's a generic hose, or the specific hose for a 67 Camaro. Regardless, a final step for installing is to turn your wheels full left and right while observing to hoses, to ensure you don't have any binding issues.