Easiest way to explain it is paint from the edge of that drivers side rear splash shield attachment lip around to the one on the passenger side in engine compartment black. Spray the face of the firewall section visible inside the front wheel well on each side allowing the overspray to mist downward while not bending down ward too much. Remember that the old spray guns produced maybe 20-30 times the amount of overspray possible with the HVLP guns today.
As you paint the inner fender panels and shock towers with a nice coat of paint with back and forth gun movement spray the outer surface of the frame rail and front cross member allowing overspray onto any mount and panels that hung down ward and again misting the bottom surface of the front frame rails. Radiator support face would normally be covered well also. With this pattern the forward and rear vertical surface of the shock towers can get a thinner though full cover of black paint also. This thinner coat can sometimes be found along the underside (shadow) of the inner panel fender lip at the top edge.
There are always differences likely produced by workers doing a little more or a little less effort which could produce runs, thin or bare spots under brackets or ledges but many of those will produce areas that will flash rust on you and produce more challenges than if you just do the job as a well intending worker having a good day would have produced
Pretty easy - typically all black
If I missed something please ask and I'll try and explain better
