I drew you a pretty picture, but photobucket is being a little bitch.

exhaust flange, 9 oclock
oil drain, 6 oclock
compressor outlet, faced towards 7 o'clock

The biggest one is the oil drain; it MUST be faced at a 6 oclock angle. Exhaust flange depends on your manifold; BEGI's cast stuff requires a 9 oclock angle, their tubular might be noon or 6 oclock. The compressor outlet is EASIEST to plumb when its at a 7 oclock angle. Mine is at a 6oclock angle and I had to cut the frame rail. 9 oclock is nearly impossible; noon is a bitch to plumb, as is 3 oclock. 4 and 5 oclock are physically impossible to plumb.