Here is a tell-tale feature of the wiring harness for the two different type of switch. Photo 1 is a shot of the old (right) and new (left) style plugs. They both have the same wires attached to them except for one important difference - the left one has a black ground wire whereas the old style does not. That black ground wire is short and is attached to the driver's door with a star washer and screw. The single door switch plugs have similar differences. The old style has only three wires attached while the late style has 5.
I got all my switches at Pick-A-Part off a 1980 Chevy Caprice wagon for $10 for 6 switches (a couple of spares!), 6 plugs, and 6 upholstery trim rings, but you can buy them new from aftermarket vendors. They are pricey - a 4-dr set will run the better part of $260 when you get the required upholstery trim rings which are sold separately.
See http://www.a1electric.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=AEOS&Product_C ode=SK7-OEGM
Thanks to Hot Rodders board member 5Window for the circuit diagram and help in solving this problem.
Installing the power window electrical circuit has been a learning experience. I had assumed that all power window motors operated the same, especially within a manufacturer's line. Not so for GM. Prior to 1980, the window motors were grounded to the door and the switch was a single pole type that sent positive current to one of the motor leads, depending on whether the window was to go up or down. Starting in 1980, the motors were electrically insulated from the door and the switch was changed to a double pole type that switched positive and ground between the two motor leads. Evidently Ford motors were of the second type from the beginning. Since I am using Ford motors and GM switches, I had to match compatibility.
Photo 1 is a schematic of the circuit. Shown are two switches, one for the drivers side with two buttons to control his and the passenger window, and a second switch for the passenger window. Obviously, to add windows, you simply duplicate the passenger circuit and add buttons to the driver's switch. The diagram shows that all of the windows have no ground circuit except one that passes through the driver master switch.
Photos 2 and 3 show how to identify the wrong pre-1980 switch and the correct 1980 one. Photo 2 is the back side of the switches. Note the correct one on top has two circuits, one for ground and one for hot. The bottom, early type does not have this feature.
Photo 3 shows the front of the switches. The one on the left is the one to look for with the shadow line on the bezel. Unfortunately they switched to chrome plated plastic for this one whereas the earlier switch was chromed metal. Nothing about the switches is interchangeable.
One last note that applies to my shortened bed. Since the front bed x-member is moved back a foot on the frame and the frame tapers there, I had to move the mounting pads out about half an inch per side. These are clamped over the x-member and held in place by 'dents'. I just drilled out the dents, slid them to place then spot welded one of the dent holes to lock it there.
The final milling step is to add all the holes in the boards. Since they are mostly held together by carriage bolts through the bed strips and through the spaces between the boards, there are surprisingly few holes to drill.
Most of the holes to drill are in the side boards that bolt directly to angle strips welded to the bed sides. DON'T trust marking these holes using the old bed boards. As shown in photo 1, clamp the boards to the angles and mark them for drilling on the press.
The other hose to drill are for the 6 long bolts that attach the bed to the frame. These have an offset 1 1/2" washer with a square carriage bolt hole. Use a Forstner bit to counter sink a 3/16" deep hole for the washer, put the washer in the hole and mark for the smaller hole and drill that with a brad point bit to pass the bolts. Photo 2.
Finally, I mounted all the x-members, boards, and bed strips on the frame to make sure they all fit properly. This is the step where I discovered the 7 1/4" boards were too wide. The entire series of boards should be exactly as wide as the bed x-members.
Those old bed strips will be replaced with polished stainless ones.