I don't think it should matter too much whether the shocks are fore or aft.Unless they are coilovers,with say..a 4-link.Forward will increase the firmness as they will be closer to the main pivot point,consequently if they are placed to the rear they will be softer.
If you are using leafs,some manufacturers use to place one front and one rear.I can only think this was to try and counteract spring wrap/torque.I dunno if this actually worked or not!
They play no part in locating the axle.The angle the shocks are placed will have an effect on the damping.
Personally I would try and keep them as upright as possible but if you have to angle them I wouldn't go much more than 10/15 degrees off vertical.Just make sure your axle is well located!!
450hp ???? MMMMM sounds like fun!


1950 Chevy Advance Design 3100 in Scotland
In the Stovebolt Gallery
More pix on Flickr.
I've definately got this truck thing in my blood ... my DNA sequence has torque settings
"Of all the small nations of this earth,perhaps only the ancient Greeks surpass the Scots in their contribution to mankind" Winston Churchill.